Chapter 5 Hydromax Reference Gives details of Hydromax' windows and each of Hydromax' menu commands. Chapter 3 Using Hydromax Explains how to use Hydromax' powerful floatation and hydrostatic analysis routines to best advantage. Chapter 4 Stability Criteria Gives details of the stability criteria that may be evaluated with Hydromax.
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. Chapter 1 Introduction Contains a description of Hydromax functionality and its interface to Maxsurf Chapter 2 Quickstart Gives a quick walk through the analysis tools available in Hydromax.About this Manual
About this Manual
This manual describes how to use Hydromax to perform hydrostatic and stability analyses on your Maxsurf design. please read the owner's manual supplied with your computer. This will introduce you to commonly used terms and the basic techniques for using any computer program. If you are unfamiliar with Microsoft Windows® interface.

.

This direct transfer preserves the three-dimensional accuracy of the Maxsurf model. The following steps are followed when performing an analysis:
Input model Analysis type selection Analysis settings Environment options Criteria specification and selection Run analysis Output
Hydromax operates in the same graphical environment as Maxsurf. Hydromax‟ analysis tools enable a wide range of hydrostatic and stability characteristics to be determined for your Maxsurf design.
Input Model
Maxsurf design files may be opened directly into Hydromax.Chapter 1 Introduction
Chapter 1 Introduction
Hydromax is a hydrostatics. Tanks and compartments can be flooded for the purpose of calculating the effects of damage. A number of environmental setting options and modifiers add further analysis capabilities to Hydromax. This allows visual checking of compartments and shows the orientation of the vessel during analysis. eliminating the need for time-consuming digitising of drawings or hand typing of offsets. stability and longitudinal strength program specifically designed to work with Maxsurf. Hydromax adds extra information to the Maxsurf surface model. margin lines and section modulus. rendering or transparent rendering. which makes it easy to use. immersion and embarkation points. centre of gravity and free surface moment.
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. the model can be displayed using hull contour lines. key points. This includes: compartments and key points such as downflooding points and margin line. The loadcase allows static weights and tankfillings to be specified and calculates the corresponding weights and centres of gravity as well as the total weight and centre of gravity of the vessel under the specified loading condition. Other input consists of: tank sounding pipes. A number of loadcases can be created. Tanks can be defined and calibrated for capacity. such as downflooding points. Hydromax is designed in a logical manner. Loadgroups may also be created and cross referenced into loadcases.

The following analysis settings are available:
Heel Trim Draft Displacement Permeability Specified condition
The analysis settings are specified prior to running the analysis. For example.Chapter 1 Introduction
Analysis Types
Hydromax contains the following analysis tools:
Upright hydrostatics Large angle stability Equilibrium analysis Specified Condition analysis KN values and cross curves of stability Limiting KG analysis Floodable Length analysis Longitudinal Strength analysis Tank Calibrations MARPOL oil outflow Probabilistic damage (Hydromax Ultimate only)
Although common analysis settings are used where possible.
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. For example: the upright hydrostatics analysis simply requires a range of drafts. whereas the longitudinal strength analysis requires a detailed load distribution.
Environment Options
Environmental options are modifiers that may be applied to the model or its environment that will affect the results of the all the hydrostatic analysis types. different analyses may require different settings. or a range of heel angles for a large angle stability analysis. The analysis settings for each analysis type are explained in detail in the analysis synopsis below. Settings that are not relevant to the selected analysis type are greyed out in the Analysis menu. a range of drafts in the case of upright hydrostatics.
Analysis Settings
The analysis settings describe the condition of the vessel to be tested.

The criterion settings and intermediate calculation data may also be displayed if required. All results are accumulated in the Report window (which can be saved.Chapter 1 Introduction
Depending on the analysis being performed. gravity and buoyancy are also displayed. complete with immersed sectional areas and actual waterlines. The centres of flotation. Heeled and trimmed hullforms and water plane shapes may be printed. Limiting KG and Floodable length analyses also use stability criteria. or output directly to a Word document. These criteria are either derived from the properties of the stability curve calculated from a Large Angle Stability analysis or from the vessel‟s orientation and stability properties calculated from an Equilibrium analysis. For a brief overview of the different analysis that Hydromax has available.
Output
Views of the hull are shown for each stage of the analysis. Results are stored and may be reviewed at any time. or as graphs of the various parameters across the full range of calculation. continue reading Chapter 2 Quickstart. different environmental options may be applied to the Hydromax:
Type of Fluid Simulation Density (of fluids) Wave form Grounding Intact and Damage condition
Stability Criteria
Hydromax has the capability to calculate compliance with a wide range of stability criteria. In addition. Hydromax has an extensive range of stability criteria to determine compliance with a wide range of international stability regulations. either in tabular form.
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. Hydromax has a generic set of parent criteria from which virtually any stability criterion can be customized. The criteria checks are summarised in tables listing the status (pass/fail) of each criterion as well as the margin. copied and printed).

.

Upright Hydrostatics Quickstart
For Upright Hydrostatics.Chapter 3 Using Hydromax
Chapter 2 Quickstart
This chapter will briefly describe each analysis type and its output.
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. Hydromax contains the following analysis types
Upright Hydrostatics Large Angle Stability Equilibrium Condition Specified Condition KN Values Limiting KG Floodable Length Longitudinal Strength Tank Calibrations MARPOL Oil Outflow Probabilistic Damage
Each analysis has different settings that may be applied
Heel Trim Draft Displacement Specified condition Permeability Loadcase Tank and compartment definition
Hydromax offers different environment options that may be applied to the analyses
Fluid Densities Treatment of fluids in tanks: fluid simulation or corrected VCG Wave form Grounding Damage
Hydromax offers an extensive range of stability criteria that are applicable to equilibrium. trim is fixed at a user defined value and draft is varied in fixed steps. limiting KG and Floodable length analysis. For each analysis type. The Analysis types section describes each of the analysis types. large angle stability. a list of the required settings as well as the available environment options is given. Displacement and centre of buoyancy and other hydrostatic data are calculated during the analysis. settings and environment options in more detail. heel is fixed at zero heel.

curves for wind heeling and passenger crowding levers and the angle of the first downflooding point. including upright GM.
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. the horizontal distance between the centres of gravity and buoyancy. the centre of gravity against the centre of buoyancy such that the trimming moment is zero. A graph of these values at the various heel angles forms a GZ curve. Large angle stability requirements
Range of heel angles to be analysed Trim (fixed or free) Loadcase or loadgroup Tank definition in the case of tank loads being included in the Loadcase (and/or for the definition of damage)
Large angle stability options
Fluid Densities Treatment of fluids in tanks: fluid simulation or corrected VCG Wave form Damage Compartment definition (in case of damage) Key points Margin line and deck edge Analysis of stability criteria
The key output value is GZ (or righting lever). Various other information is often overlaid on the GZ curve. These additional data depend on which (if any) stability criteria have been selected.Chapter 3 Using Hydromax
Upright hydrostatics requirements
Range of drafts to be analysed VCG (for calculation of some stability characteristics such as GMt and GMl only) Trim
Upright hydrostatic options
Fluid Densities Wave form Damage Compartment definition (in case of damage)
The results are tabulated and graphs of the hydrostatic data. A range of heel angles are specified and Hydromax calculates the righting lever and other hydrostatic data at each of these heel angles by balancing the loadcase displacement against the hull buoyancy and. For more detailed information please see: Upright Hydrostatics on page 78. if the model is free-to-trim. curves of form and sectional area at each draft are available. displacement and centre of gravity are specified in the loadcase.
Large Angle Stability Quickstart
For the analysis of Large Angle Stability.

as is the freeboard to any defined key points. If a wave form has been specified there will be a number of columns. to calculate the displacement and the location of the centre of gravity.
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. margin line and deck edge will also be computed and tabulated. Maximum safe steady heel angle The sectional area curve at each of the heel angles tested may also be displayed.Chapter 3 Using Hydromax
A number of other graphs may be selected from the pull-down list in the graph window. Remember that you can access this data in tabular form by double clicking in the graph window:
Dynamic stability curve (Area under GZ curve. these results will also be reported in the criteria results table and they may lead to additional curves being displayed on the GZ curve. each column contains the results for a different position of the vessel in the wave as given by the wave phase value. Any equilibrium criteria will also be evaluated and their results reported. integrated from upright) Variations of other hydrostatic and form parameters may be plotted against heel angle.
Equilibrium Condition Quickstart
Equilibrium Analysis uses the Loadcase. Hydromax iterates to find the draft. Downflooding angles for any key points. For more detailed information please see: Large Angle Stability on page 80.
Note that some of these graphs have parameters that may be adjusted in the Data Format dialog If large angle stability criteria have been selected for analysis. Equilibrium analysis requirements
Loadcase or loadgroup Tank definition in the case of tank loads being included in the Loadcase (and/or for the definition of damage) Compartment definition and damage case (in case of damage)
Equilibrium analysis options
Fluid Densities Treatment of fluids in tanks: fluid simulation or corrected VCG Wave form Grounding Damage Compartment definition (in case of damage) Key points Margin line and deck edge Analysis of equilibrium criteria
Equilibrium analysis result table lists the hydrostatic properties of the model. The sectional area curve is also calculated. heel and trim that satisfy equilibrium and reports the equilibrium hydrostatics and a cross sectional areas curve. margin line and deck edge.

They may be calculated for a number of displacements before the height of the centre of gravity is known.
Specified Condition Quickstart
In the specified condition each of the three degrees of freedom. can be set. For more detailed information please see Specified Conditions on page 90. and KG is the distance from the baseline to the vessel's effective Vertical Centre of Gravity. you may enter the trim or specify the forward and aft drafts (these are at the perpendiculars as specified in the Frame of Reference dialog). Specified Condition Requirements
Specified Conditions Input Dialog
If fixed trim is specified.
KN Values Quickstart
KN values or Cross Curves of Stability are useful for assessing the stability of a vessel if its VCG is unknown. KN Values Analysis Requirements
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.KG * sin(Heel) where GZ is the righting lever measured transversely between the Centre of Buoyancy and the Centre of Gravity. for which the hydrostatic properties of the model are to be calculated. The KN data may then be used to obtain the GZ curve for any centre of gravity height (KG) using the following formula: GZ = KN . Specified Conditions options
Fluid Densities Wave form Damage Tank and Compartment definition (in case of damage)
The output for the specified condition consists of a curve of cross sectional areas and hydrostatics of the vessel in the specified condition.Chapter 3 Using Hydromax
For more detailed information please see: Equilibrium Analysis on page 87.

For more detailed information please see KN Values Analysis on page 92. Hydromax runs several Large Angle Stability analyses at different KGs.
Limiting KG Quickstart
The Limiting KG analysis may be used to obtain the highest vertical position of the centre of gravity (maximum KG) for which the selected stability criteria are just passed. If the analysis is performed free-to-trim and an estimate of the VCG is known. This may be done for a range of vessel displacements.Chapter 3 Using Hydromax
Range of displacements to be analysed Range of heel angles to be analysed Trim (fixed or free) Estimate of VCG (provides more accurate result if free-to-trim) TCG (if required)
KN Values Analysis Options
Fluid Densities Wave form Damage Tank and Compartment definition (in case of damage)
Output is in the form of a table of KN values and a graph of Cross Curves of Stability. The computed KN results will then give a more accurate estimate of GZ for KG close to the estimated VCG since the effects of VCG on trim have been more accurately accounted for. At each of the specified displacements. the centre of gravity is increased until one of the criteria fails. this may be specified. Limiting KG Analysis Requirements
Range of displacements to be analysed Range of heel angles to be analysed Trim (fixed or free) Stability criteria for which limiting KG is to be found TCG (if required)
Limiting KG Analysis Options
Fluid Densities Wave form Damage Tank and Compartment definition (in case of damage) Laodcase (in case of initial loading of damaged tanks) Key points (if required for criteria) Margin line and deck edge (if required for criteria)
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. The selected stability criteria are evaluated.

Some criteria. the LCG may be specified directly or calculated from a specified initial trim. Only relevant criteria will be used. A check will be made to ensure that any selected equilibrium criteria are passed.Chapter 3 Using Hydromax
A graph of maximum permissible GZ plotted against vessel displacement is produced as well as tabulated results indicating which stability criteria limited the VCG. such as angle of maximum GZ. In addition a range of permeabilities may be specified. are very insensitive to VCG and may prevent the analysis converging. If limiting curves are required for each of the stability criteria individually. if the intact condition is used. this may be done in the Batch Analysis mode. The VCG is also required to ensure accurate balance of the CG against the CB at high angles of trim. only damage criteria will be evaluated.
Floodable Length Quickstart
This analysis mode is used to compute the maximum compartment lengths based on user-specified equilibrium criteria. Floodable Length Analysis Requirements
Range of displacements to be analysed VCG Range of permeabilities to be analysed Trim (free.to. i. Floodable Lengths may be computed for a range of displacements. only intact criteria will be evaluated.trim to either initial trim or specified LCG) Floodable length criteria to be tested
Margin line and deck edge (required for criteria)
Floodable Length Analysis Options
Fluid Densities Wave form
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.e. however at least one large angle stability criterion is required. As well as the standard deck edge and margin line immersion criteria (one of which must be specified) the user can also add criteria for maximum trim angle and minimum required values of longitudinal and transverse metacentric height. if a damage case is chosen. If the analysis is unable to converge for a certain displacement this will be noted and the next displacement tried. For more detailed information see Limiting KG on page 95.

centre of gravity and free surface moment (FSM). For more detailed information please see Longitudinal Strength on page 105. graphs of allowable shear and bending moment are superimposed on the graph. For more detailed information please see Floodable Length on page 102. soundings are measured from the bottom of the sounding pipe to the free surface.
Tank Calibrations Quickstart
Tanks can be defined and calibrated for capacity. If defined. Tabulated results may be customised using the Data Format dialog:
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. Hydromax uses its fluid simulation mode to calculate the actual position of the fluids in the tanks. Longitudinal Strength Analysis Requirements
Loadcase (including distributed loads if required) Tank definition in the case of tank loads being included in the Loadcase (and/or for the definition of damage)
Longitudinal Strength Analysis Options
Fluid Densities Treatment of fluids in tanks: fluid simulation is always used for Longitudinal Strength analysis Wave form Grounding Damage Compartment definition and damage case (in case of damage) Allowable shear and bending moment
The longitudinal strength graph and tables contain all information on weight and buoyancy distribution. The results for a single condition are shown in the results table. the shear force and bending moment on the vessel. Tank ullages are measured from the top of the sounding pipe to the free surface of the liquid within the tank along the sounding pipe and in a similar manner. i. taking into account the vessel trim and heel. The condition to be viewed may be selected from the Results toolbar.
Longitudinal Strength Quickstart
Hydromax calculates the net load from the buoyancy and weight distribution of the model. The data is tabulated for each of the stations as defined in Maxsurf. The data is also presented graphically. Tank calibrations may be calculated for a range of trim and heel angles.e. Tank calibrations may be performed for a range of heel and trims. the position of the fluid in the tank will be computed so that the fluid surface is parallel with the external seawater surface. That data is then used to calculate the bending moment and shear force on the vessel.Chapter 3 Using Hydromax
The output is in the form of tabulated Floodable Lengths for each displacement and permeability. Fluid densities and tank permeabilities can be varied arbitrarily.

It is possible for this data to become corrupted.
Windows Registry
Certain preferences used by Hydromax are stored in the Windows registry. The following preferences are stored in the registry:
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. then follow the instructions on screen. You will be asked if you wish to clear the preferences. or you may simply want to revert back to the default configuration. To clear the Hydromax preferences. doing this will reset all the preferences. Note: Before installing any program from the Maxsurf suite for the first time. Hydromax should be accessible through the Start Menu. please read the purchase letter (also referred to as installation manual). click OK.Chapter 3 Using Hydromax
Chapter 3 Using Hydromax
This chapter describes
Getting Started Hydromax Model Analysis Types Analysis Settings Analysis Environment Options Analysis Output
Getting Started
This section contains everything you need to do to start using Hydromax
Installing Hydromax Starting Hydromax
Installing Hydromax
Install Hydromax by inserting the CD and running the Setup program. Simply select Hydromax from the Maxsurf menu item under Programs in the Start menu. start the program with the Shift key depressed.
Starting Hydromax
After installation.

you may need to set up the following additional model data:
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.Chapter 3 Using Hydromax
Colour and line thickness settings of contours and background Fonts Window size and location Size of resizing dialogs (alternatively. Check the density of seawater after resetting your preferences.
Hydromax Model
This section describes how to open a Maxsurf model in Hydromax and provides some important information to ensure that your model is correctly interpreted by Hydromax.
Setting Initial Conditions
Depending on the analysis performed. the next step is to check the Hydromax settings and initial analysis conditions.
Preparing a Design in Maxsurf Opening a New Design Opening an Existing Hydromax Design File Updating the Hydromax Model Hydromax Sections Forming Checking the Hydromax model
After checking the Hydromax model. KN and Limiting KG analyses Permeabilities for floodable length analysis Location of files Units for data input and results output Convergence tolerance (Error values) Maximum number of loadcases Reporting preferences
Note: The default density for the fluid labelled "Sea Water" is stored in the windows registry. these may be reset by holding down the shift key when activating them) Density of fluids Heel angles for large angle stability. All hydrostatic calculations use this. It is recommended to save your customized densities with your project using the File | Save Densities As command.

However it is possible to specify upto nine additional locations at which the drafts should be reported. the vessel‟s bow is on the right. By convention. midships is automatically defined midway between the perpendiculars. A consistent zero point and frame of reference should be used for the model throughout the Maxsurf suite. Down Flooding Points) Margin Line Points Modulus Points and Allowable Shears and Moments Stability Criteria
Preparing a Design in Maxsurf
There are several important checks that must be carried out in Maxsurf before opening a design in Hydromax:
Setting the Zero Point Setting the Frame of Reference Surface Use Skin Thickness Outside Arrows Trimming Coherence of the Maxsurf surface model
Setting the Zero Point
Ensure that the zero point is correctly setup in Maxsurf. The frame of reference cannot be changed in Hydromax. In Hydromax you have the option of displaying longitudinal measurements such as LCB or LCF from the model zero point or amidships.g. The frame of reference defines the fore and aft perpendiculars. in the profile and plan views. The Frame of reference should not be changed in Hydromax. This is done through the Data | Draft Marks dialog.Chapter 3 Using Hydromax
Working with Loadcases Modelling Compartments Forming Compartments Compartment Types Damage Case Definition Sounding Pipes Key Points (e.
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. the baseline and the datum waterline. The perpendiculars define the longitudinal positions of the vessel‟s draft marks and cannot be coincident.
Setting the Frame of Reference
It is vital that the Frame of Reference is correctly setup in Maxsurf before attempting to analyse the model in Hydromax. The base line is the datum from which the drafts and KG are measured.

Thickness can be specified differently for each hull surface.
Skin Thickness
Hull Shell
Internal Structure
If skin thickness is to be used in hydrostatic calculations.Chapter 3 Using Hydromax
Note: Draft and Trim specification It should be remembered that the drafts specified for an analysis are the drafts at the perpendiculars (or amidships) and the trim specified (and reported) is the difference between the draft at the AP and draft at the FP. the internal structure surface should be placed to model the inside of the tank if the tank wall has significant thickness. Skin thickness for hull surfaces will be treated so that the hull sections go to the outside of the plate whilst any tanks are trimmed to the inside of the plate.
Surface Use
In Maxsurf you can choose between two types of surface use Hull Hull surfaces are used to define the watertight envelope of the hull. Internal structure Internal structure surfaces are used for all other surfaces (any surfaces which do not make up the watertight envelope) and also surfaces which are to be used in Hydromax to define the boundaries of tanks and compartments that have complex shapes. If a surface is defined as internal structure. ensure that the thickness and projection direction have been specified for the hull shell surfaces. internal surfaces will be ignored in the forming of hydrostatic sections. To activate skin thickness in Hydromax ensure that the “Include Skin Thickness” option is selected when reading the file or calculating the hull sections.e. The following table describes the difference between each surface use in Hydromax: Included: Hydrostatic sections Selection of tank/compartment boundaries Skin thickness applied to the surface Verify that all surfaces that are to be used as tank/compartment boundaries are defined as Internal Structure. i. Note Tank boundaries made from internal structures surfaces do not have skin thickness. resulting in more accurate hydrostatics. To include skin thickness.
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. it is not included as part of the hull shell by Hydromax.

Chapter 3 Using Hydromax
Outside Arrows
The surfaces‟ outside arrows define the orientation of the surfaces. the deck).
Correct section with one opening: this section will be closed across the top. At any longitudinal position on the hull. you should have completely closed transverse sections or sections with at most one opening (e.
Correct Section with no opening. Ensure that you have used the Outside Arrows command from the Maxsurf Display menu to define which direction points outwards (towards the seawater) for each surface. The surface direction may be flipped by clicking on the end of the arrow.
Trimming
Ensure that all surfaces are trimmed correctly.
Also see: Hydromax Sections Forming on page 27 Checking the Hydromax model on page 30
Coherence of the Maxsurf surface model
Hydromax will generally have no problem correctly interpreting your design as long as the following requirements for the Maxsurf model are observed:
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.g.

e. Also see: Checking the Hydromax model on page 30. The following dialog will appear:
Calculate new Sections
Choosing Calculate Sections will calculate the specified number of sections through the hull. if any) is explained in Opening an Existing Hydromax Design File. any surface thickness specified in the Maxsurf Surface Properties dialog may be included. the part of the keel that is inside the hull and the part of the hull that is inside the keel Do not have surfaces that cannot be closed in an unambiguous fashion. then select Open Design from the File menu. e. preferably by bonding the edges together Where surfaces intersect. trim away the excess regions of the surface. i. i. internal structure surfaces are ignored when forming the hull sections in Hydromax
Note: For groups internal structure surfaces that will be used to define tank (or compartment boundaries) the same requirements apply.
Use Trimmed Surfaces
If the Maxsurf model has trimmed surfaces.
Include Plating Thickness
At this stage. These will then be used for the Hydrostatics calculations.e. a maximum of one gap in a transverse section through the hull. Hydromax will automatically look for compartment definition files when you are in a Compartment Definition window and a loadcase in a Loadcase window. Choose a Maxsurf design file (. To open a design for analysis. the Use Trimmed Surfaces item should be ticked.msd).Chapter 3 Using Hydromax
Make sure that each surface touches its adjacent surfaces at its edge. The meaning of (ignore existing data. Remember that the inner portions of each intersecting contour will be trimmed off Check surface use.g.
Opening a New Design
File opening in Hydromax is window specific.
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. ensure that the design view window is active.

compartment definition. by specifying one station 1mm aft of amidships and one station 1mm forward of amidships this discontinuity can be modelled very accurately. sounding pipes etc. there are two options:
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.msd).
Surface Precision
The Surface Precision options has two functions:
Setting for calculating the hydrostatic sections Setting used to form new compartments or tanks.
Opening an Existing Hydromax Design File
After saving the Maxsurf design file for the first time in Hydromax. key points. The first option allows you to use the station grid created in Maxsurf. For example. This is extremely useful for hulls that have features such as keels or bow thrusters that need to be accurately modelled and may need a locally denser station spacing to do so. Note: Maxsurf surface trimming information may vary for different precisions.hmd) is created. avoiding any errors inherent in the integration of evenly spaced stations. Reducing the precision of the sections can greatly improve performance. To open an existing design.Chapter 3 Using Hydromax
Stations
When calculating stations.
The precision at which the design was saved in Maxsurf is included in the Maxsurf design file (. a “Hydromax Design file” (. Reducing the number of stations will speed up the analysis time but reduce the accuracy. Hydromax recognises this precision setting and will and set the Surface Precision button accordingly. if it was known that a design had a significant discontinuity in its sectional area curve at amidships.
Note: The accuracy of the results depends much more on the number of sections than the accuracy at which the sections are calculated. It also allows designs with significant longitudinal discontinuities in their sectional areas to have stations specified either side of the discontinuity. conversely increasing the number of stations will increase the analysis time but lead to higher accuracy results. usually at relatively small impact on the accuracy of the hydrostatics. you may select how many stations should be used. The Hydromax design file will consist of the hydrostatic sections and all input data such as loadcases. The upper limit for the number of stations is 200. Hydromax also allows saving of all input and output files into individual files. Therefore it is recommended not to change the precision setting when opening the Maxsurf design file in Hydromax.

msd file.hmd file was saved. Notes: 1) When selecting “Read existing data and sections (do not update geometry)” the Maxsurf surface information is not recalculated.msd. are not automatically incorporated. The Calculate Sections dialog now has the option to read the sections from the file.hmd file from any Windows explorer window Use the Hydromax Open command form the file menu and select the . key points etc.e.
When Hydromax opens a .
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. compartment definitions.Chapter 3 Using Hydromax
Double click on the . the OSV.msd file.

Ensure “Read existing data and sections” is selected and click OK. it will look for a . For example: when opening OSV. This contains hydrostatic sections information and all input information from last time the . This means that changes to the hull shape in the Maxsurf Design file. i. See: Updating the Hydromax Model on page 26 for more information.hmd file. damage cases. loadcases and compartment definitions etc. You will load your existing sections.hmd file is found. loadcases.msd file
An existing Hydromax design consists of a number of files with different file extensions.
Hydromax will now open the .hmd file with the same name as the .

the tanks and centre of gravity (from the loadcase) have remained in their same locations relative to the zero point. Etc. if any) means that Hydromax will recalculate the hull sections and ignore any data stored in the .
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. In the second image. In previous versions of Hydromax this could cause problems because the loadcase and tank data maintained their position relative to the zero point. Note that whilst the margin line and key points have remained in their same locations relative to the hull. the zero point has been moved (in Maxsurf) to the aft-perpendicular and the DWL. data is defined in Hydromax. The first image shows the model as initially defined in Hydromax with the zero point amidships and at the baseline. The two images from Hydromax 13 show this problem.hmd file. Do not choose this option if you wish to keep the additional Hydromax data and you have not yet saved them as individual files as if the model is saved in Hydromax the .
Original location of data as entered in Hydromax before zero point change in Maxsurf. data is then created in Hydromax and that data all saved in the .
Hydromax 13 behaviour
It may sometimes occur that the model zero point location is changed in Maxsurf after tank.hmd file. The model is closed in Hydromax The model is opened in Maxsurf and for some reason the location of the zero point is changed The model is reopened in Hydromax and the tank and load etc. where as the key points and margin line remained in the same position relative to the hull. data is automatically read from the . You will have to reload your individual loadcases and compartment definition files etc after you have selected this option and pressed OK.hmd file will be overwritten and any existing data lost. please see: File Extension Reference Table on page 307.hmd file (as is done when you chose Save when the drawing window is top most). For more information on file properties and extensions in Hydromax. loadcase.
Effect of Zero Point change
The description below relates to what happens in the following situation:
A hull model is generated in Maxsurf Tank and load etc.Chapter 3 Using Hydromax
2) Calculate new sections (ignore existing data.

Note that this is only possible with Hydromax models that have been saved from the new version of Hydromax (because the new version of Hydromax now saves the zero point independently so that it can check for changes).hmd file. if the zero point has changed.Chapter 3 Using Hydromax
Effect of Zero point change in Maxsurf 13. when loading a .
Selecting “yes” will maintain the position all the Hydromax data relative to the hull. This of course means that the numerical values of the various data are changed:
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.
Original location of data as entered in Hydromax before zero point change in Maxsurf. Hydromax will display the following message:
If the zero point is moved in Maxsurf. Hydromax 14 behaviour
To rectify this problem. Hydromax now detects if the zero point has been modified in Maxsurf when the model is reopened in Hydromax. essentially just the zero point it moved.
Now. you will now be prompted.

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. Thus the tanks and loads etc. but their numerical values will remain the same: The example shown is quite extreme. Any tanks and loadcases will also be updated with this command.
Click “no” to maintain position relative to zero point. This function can also be used to include/exclude surface thickness or change the number of sections and to change use/not use trimmed surfaces without reloading the Maxsurf Design File.
Selecting “no” will move all data other than the margin line with the zero point.
Updating the Hydromax Model
To update the hydrostatic sections to the latest Maxsurf Design File. The “Recalculate Hull Sections” command recalculates Hull surfaces as well as Tank Boundary surfaces (Internal Structure surfaces in Maxsurf). it is more likely that this option would be selected if it was realised that the zero point for the tank plan were slightly different than the zero point of the lines plan and a small correction to the zero point was required.Chapter 3 Using Hydromax
Click “yes” to maintain position of tanks. select “Recalculate Hull sections” in the analysis menu after reloading the Maxsurf Design File with the “read existing data and sections from file” option selected. will move relative to the hull. loads etc relative to the hull.

Hydromax will automatically form these sections. an ambiguity exists as to how the two line segments will be connected. using “Read existing data and sections” to make sure the loadcase. contours cannot be contained wholly within another contour. Hydromax deals only with sections that are completely closed. Note: The golden rule is that for any longitudinal position. Whilst it is always preferable to give Hydromax a completely closed model with no ambiguities. Hydromax will automatically close the section with a straight line connecting the opening ends. (e. Hydromax will try to resolve any problems with the model definition in the manner outlined in the following sections. a hull surface with no deck). the section must be made up of closed. non-intersecting (and non-self-intersecting) contours.g. it is necessary to: 1) save and close the model in Hydromax 2) save in Maxsurf 3) open in Hydromax. Furthermore.
Hydromax Sections Forming
Hydromax works by applying trapezoidal integration to data calculated from a series of cross sections taken through the Maxsurf model surfaces. The same is true for groups of internal surfaces that have been selected to define a tank boundary. or can be unambiguously closed.
Where a section consists of an open shell (e.g. one opening is acceptable and this will be automatically closed with a straight line. This is not an acceptable shape.Chapter 3 Using Hydromax
Note: Changes to the Maxsurf design are only recalculated after the new Maxsurf design has been re-loaded into Hydromax. In practice. “hydrostatic sections” or just “sections”. having both a gap at the centreline as well as an open deck). called “Hydromax sections”. compartment definition etc remain part of the Hydromax design file. however. This section outlines the section forming process used in Hydromax and may be helpful when preparing a Maxsurf design for Hydromax. This means that if the model is simultaneously being edited in Maxsurf and Hydromax.
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. the section is made up of two line segments. 4) use the “Recalculate Hull Sections” from the analysis menu.
If.

Hydromax will form a closed section through multiple surfaces by linking the curve segments together.
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. bonded together or use compacted control points will not cause any problems when opened in Hydromax. Multiple surfaces that are trimmed correctly. if either the top or bottom gap had been closed in Maxsurf the design would cease to be ambiguous.Chapter 3 Using Hydromax
In the example above.

Where surfaces intersect. Hydromax will have difficulties distinguishing the intended main deck. The user cannot change these tolerances. Hydromax will make an attempt to remove excess portions of the curve to form a single continuous contour. However this is not always possible so it is much better practice to trim the model correctly manually.Chapter 3 Using Hydromax
A section through a multihull containing a single closed contour
A section comprising two closed contours
Hydromax will link curve segments together if they are only separated by a small amount.
Hydromax closes the outside contour and trims remnants
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. decks. because there are too many dependencies in the program. bulwarks)
A common example of ambiguous sections is a model with multiple decks.g.
Ambiguous Sections (e.

Therefore. These sections should be continuous with no gaps and no unexpected lines. In particular. Incorrect sections in the model will give incorrect results.Chapter 3 Using Hydromax
The example above has bulwarks. the left and right arrow cursor keys will enable you to step through the sections one-by-one. look closely at intersections between surfaces to make sure that Hydromax has interpreted the shape correctly. For more information see the Maxsurf manual. To prevent ambiguities it is recommended to trim the bulwark in Maxsurf.
Checking the Hydromax model
Before starting any analysis you should check whether Hydromax has been able to correctly interpret your design. The following tools are available to validate the Hydromax model. checking your sections after opening the design in Hydromax is strongly recommended. This is done by selecting Show Single Hull Section in Body Plan view from the Display menu. you can step through the sections one-by-one to verify that they have been correctly calculated. generally these will be treated correctly by Hydromax and removed.
Show Single Hull Section
In the body plan view. but this depends on the height of the bulwark relative to the rest of the section.
Show Single Hull Section Checking the Sectional Area Curve Using Rendering to Check the Model
Note: Sections that are not formed correctly cause the majority of problems with Hydromax models. You can then click in the inset box to view the sections.
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. This works the same as the Maxsurf body plan window and is an extremely powerful tool to validate your Hydromax model. If the bulwark‟s volume is expected to influence the hydrostatic calculations. the bulwark‟s volume has to be properly modelled in Maxsurf by modelling both the outside and the inside of the bulwark.

This Cross Sectional Area curve indicates there may be a problem with section forming from 12 m to 16 m. which makes it easier to see if there are any areas of the model which have not been properly defined.Chapter 3 Using Hydromax
Checking the Sectional Area Curve
Another way of checking the Hydromax model is to perform a specified condition analysis at quite deep draft and look carefully at the sectional area curve in the graph window. Select Render from the Display menu whilst in the perspective view and turn on the sections:
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. Using Rendering to Check the Model
The model may also be rendered. If this displays any unexpected spikes or hollows Hydromax may not have correctly interpreted the hull shape. This is not a foolproof method since it does not necessarily highlight problems in the non-immersed part of the hull.

Further detailed checking of hull and tank/compartment sections
When checking that your model is correct. To do this go to the body plan view in Hydromax and select “Show Single Section”:
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. the model is correct. you are interested in whether the sections are correct.Chapter 3 Using Hydromax
Note: In rare instances incorrect rendering may occur. As long as the sections are formed correctly. This does not necessarily mean that the model is incorrect.

Chapter 3 Using Hydromax
Then to check that the tanks are OK. leave the view as it is. but turn on the visibility of all the tanks of interest (if there are few tanks. only tank sections near the current hull section are shown:
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. then you can show all of them. In the single section view. if there are many it may help to hide some and check a few at a time).

Hydromax uses the aft perpendicular and forward perpendicular together with the baseline and the zero point for all calculations and gives the results in the units specified in the display menu. it is important that you set up the required initial conditions for the design.Chapter 3 Using Hydromax
Setting Initial Conditions
All Hydromax calculations are performed in the frame of reference of the model.
Coordinate System
Hydromax uses the Maxsurf coordinate system:
Longitudinal Transverse Vertical View window
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+ve forward +ve starboard +ve up View direction
-ve aft -ve port -ve down
. Note: Before you run any analysis using Hydromax.

This is done through the Data | Draft Marks dialog. This should be done in Maxsurf and not in Hydromax. some analysis results will be meaningless or may even fail to complete. Port side above the centreline (this the opposite direction to Maxsurf) From Starboard. See: Setting the Zero Point and Setting the Frame of Reference on page 18. Note: Changing the zero point in Maxsurf will not update the compartment definition. loadcase and other input values. Draft and trim are measured on the forward and aft perpendiculars. Drafts are always measured to the Baseline in the centre plane of the vessel. bow to the right.
Draft Marks
Drafts are automatically calculated at the perpendiculars and amidships. If these are not in the correct positions. Changing the zero point after you have started analysing the model in Hydromax is not recommended. Immersed depth measurements are made perpendicualar to the free-surface. looking fwd From above.Chapter 3 Using Hydromax
Body plan Plan Profile
From the stern.
Difference between “Immersed depth” and “Draft” measurements
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. you may specify upto nine additional locations at which the drafts should be reported. should you require drafts to be calculated at other locations.
Frame of Reference and Zero Point
It is essential that a frame of reference be specified.

e.
User-defined draft locations and new toolbar button
Note: Draft and Trim specification It should be remembered that the drafts specified for an analysis are the drafts at the perpendiculars (or amidships) and the trim specified (and reported) is the difference between the draft at the AP and draft at the FP. Prismatic and Waterplane Area Coefficients.
Customising Coefficients
In Hydromax you may choose between the length between perpendiculars and the waterline length for the calculation of Block. Drafts can only be defined when the vessel is rotated to the DWL (Display | Set vessel to DWL).Chapter 3 Using Hydromax
User-defined Draft Marks
Note that the Trim is still defined as the difference between the drafts at the perpendiculars and the Midship draft (used to define the range of immersions for the Upright Hydrostatics analysis) is the mean of the drafts at the perpendiculars. Finally you can chose whether you want the LCB and LCF to be displayed as a length or as a percentage of the waterline or LPP length as specified in the Length for Coefficients. Aft Perpendicular. You can also specify whether you want the forward (towards the bow) or the aft (towards the stern) to have a positive sign. You may also select the draft. neither of these values has changed and neither are affected by the user-defined draft locations.
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. The LCB and LCF can be displayed in the Results windows relative to the specified Zero Point. Amidships location. beam and sectional area to be used for calculation of these coefficients. Middle or fwd end of the actual waterline. Fwd Perpendicular or from the Aft. i.

The angular units for measuring heel and trim angles are always degrees. units for force and speed (used in wind heeling and heeling due to high-speed turn etc.
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. In addition to the length and weight (mass) units.Chapter 3 Using Hydromax
Data | Coefficients dialog Setting Units
The units used may be specified using the Units command. may also be set. Units may be changed at any time. criteria) and the angular units to be used for areas under GZ curves.

Loadgroups are special loadcases that contain no tanks. click on the update Loadcase button and ensure that the hull is at the DWL by selecting “Set vessel to DWL”:
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. A loadgroup is included in a loadcase simply by specifying the loadgroup name in the “Item Name” column. Loadcases automatically contain all the tanks defined in the Tank definition. These may be used to define groups of fixed weights (such as the steel weight or lightship weight) in a single location which may then be cross-referenced into a loadcase. The loadcase will normally update the column totals automatically as weights or tank loadings are changed. Any changes to the loadgroup are then automatically incorporated into any loadcases that reference them. If the loadcase does not update. The exception to this is if tanks have not yet been formed or the vessel is still rotated from the result of an analysis. expressed as either a percentage of the full tank capacity or as a weight. Static weights that make up the vessel lightship are specified here as well as tank filling levels.Chapter 3 Using Hydromax
Other Initial Conditions
See: Fluids Analysis Methods on page 148 Density on page 150
Working with Loadcases
Loadcases define the loading condition of the vessel.

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. switch to the loadcase view by selecting Loadcase from the Loadcase sub-menu in the Window menu. Then select “New Load Case” from the File menu or press Ctrl+N. A new load spreadsheet will be displayed in the Loadcase window.Chapter 3 Using Hydromax
The individual loads can be displayed graphically:
Creating a new Loadcase File
To create a load case. The default loadcase will contain a lightship entry and an entry for each tank (with a default filling of 50%).

To do this. select the Loadcase you wish to use as a template
Bring the loadcase you wish to use as a template to the front for example by clicking on the tab on the bottom 
select File | New
First. you will be asked for a new Loadcase name after which the following dialog appears:
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.

In the loadcase window. an existing loadcase may be used as a template when creating a new loadcase.Chapter 3 Using Hydromax
The tabs in the bottom of the window can be used to skip through the different loadcases in the design.
Create New Loadcases based on Template
To avoid rework.

The next time you use the File | Save Loadcase command you will be asked to confirm the loadcase file name. Number of Loadcases command.
Loading a Saved Loadcase
You can load a saved loadcase into your loadcase window by:

Select an empty tab in the loadcase window that you wish to load the loadcase into
Empty tab. you should either increase the maximum number of loadcases (see below). you will either have to close an existing loadcase. or close an existing loadcase. Alternatively. Note The template is only used during the creation of the loadcase. Once a loadcase has been created from a template loadcase.

Select File | Open Load Case
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.
Naming and Saving a Loadcase
A loadcase can be given any name by saving it to a separate file where the loadcase filename will be used as the loadcase name and displayed on the tab in the loadcase window. If there are no blank tabs left.

Select Edit Loadcase from the Case menu

Changing the name in the Loadcase Properties dialog. changes made in the template are NOT automatically changed in the loadcase derived from it. or add more loadcases using the Case | Max.Chapter 3 Using Hydromax
A new loadcase will appear in one of the blank (…) loadcase tabs.
If there are no empty tabs.

and press the Tab key to go to the next column in the table (or simply click directly in the cell you wish to edit). This is used to calculate the total weight of that item.Chapter 3 Using Hydromax

Select the .
Editing Loads
Click on the cell containing the load name and type in a name for this load. you will only need to set this once to the maximum number of loadcases you are ever likely to use. If you wish to delete several loads simultaneously. Each loadcase can be selected and used for analysis. then select Delete Load. Number of Loadcases” from the Case menu. and choose Delete Load from the Edit menu (or highlight the complete row by clicking the grey cell to the left of the row and press the Delete key). The weight of each item should be entered in the next column. In most cases. a sensible number is recommended. You can repeat this process for as many loads as you wish. For each item in the list you can specify a quantity.hml file you wish to open. and the total weight of crew would be automatically calculated. effectively allowing you as many loadcases as you require. For convenience of use.
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.
A new load will be inserted into the table above the currently selected row.
Setting the Maximum Number of Loadcases
The maximum number of loadcases (up to twenty-five) that can be loaded in Hydromax at any one time is set by selecting “Max. You may then enter the maximum number of load cases you require. for example "Lightship".
You must restart Hydromax for this change to take effect. you will receive a warning and the file will not be loaded.

Select Add Load from the Edit menu or press Ctrl+A.
Closing a Loadcase  
Select the tab of the loadcase you wish to close in the Loadcase window Select File | Close Load Case
Adding and Deleting Loads
To add an extra load to the loadcase. Each may be saved and loaded independently. If you want to remove a load from the table. You must increase the maximum number of allowable loadcases and restart Hydromax before you can load the design. you could specify the quantity and unit weight. simply click anywhere in the row you want to remove. For example: if the item was “crew” with a weight per unit. click and drag so that all of the loading rows that you wish to delete are selected. Note: When loading a design that has more loadcases than the maximum you have currently set in Hydromax.

Insert row | Delete row | Sort rows | Move row(s) up | Move row(s) down
Sort selected columns
After moving loads. Hydromax does this automatically prior to running an analysis.Chapter 3 Using Hydromax
The weight must always be positive. To ensure data consistency. are measured from the Zero Point.) character in the Item Name field. Longitudinal Strength or Equilibrium analysis are selected. After you type in this number. The CG position will also be shown and updated in the View windows if Large Angle Stability.
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. Adding Component or Heading Lines Components or headings can be included in a load case by preceding the text with a period (.
Loadcase Sorting
A number of tools are available for controlling the order in which items and tanks occur in the loadcase. you can do so by entering a negative quantity – this can be useful if you want to apply a pure moment to the model by applying equal magnitude. press enter and the total LCG will be automatically re-calculated and displayed in the bottom row of the table. you may have to use Analysis | Update Loadcase ( button) to update the subtotals and subsubtotals. but opposite sign loads to the vessel in the loadcase. heading or sub-total lines in the table. fluid type (for tanks) etc. Tab to the next column and enter the horizontal lever for the item. apostrophe („) or full-stop(. subtotals and subsubtotals.) character. You may move selected items and tanks up and down in the loadcase.
Loadcase Formatting
Hydromax allows you to improve the presentation of the Load Case window by adding blank. If for some reason you wish to have an upward (negative) load. Note: Levers. as with all other measurements in Hydromax. you may also sort selected items by name. Adding Blank Lines A blank line can be added into the load case by placing a dollar ($).

Quantity and Unit mass for sub total rows
If a sub total includes only tanks.Chapter 3 Using Hydromax
Adding Totals or Subtotals A subtotal can be displayed for several loads within a load case.

View | Colours and lines menu when Loadcase window is frontmost
Loadcase format
It is possible to select which columns are displayed in the loadcase window. Use the Display | Data Format dialog:
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. To do this the item name field must commence with the word „total‟ or „subtotal‟. then the quantity and unit mass items will be included. When tanks are grouped by fluid type this can be useful for calculating the total tank capacity for that fluid type. tanks may be displayed in the same colour as the fluid they contain (As defined in Analysis | Fluids dialog). The unit mass is the sum of all the masses of the full tanks and the quantity is the sum of the masses divided by the sum of the full tank masses. Sub-subtotals Sub-sub-totals may also be inserted. Grouping Similar Tanks Use the move items UP or Down commands in the Edit menu to adjust the row order in the loadcase. alternatively. Sub-subtotals must start with the text “subsubtotal”.
Loadcase Colour Formatting
Different colours can be defined for fixed mass items and tanks.

the fore and aft limits define the longitudinal extents of the load. This can be useful for vessels such as product carriers which may have cargos of different types of fluids with different densities.
If the longitudinal arm is changed in the Loadcase window. Arm” column defines the longitudinal position of the centre of the load.
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. the forward and aft limits will be moved by the same amount. the centre of gravity should be midway between the forward and aft limits. For an evenly distributed load. The “Long.
Longitudinally Distributed Loads
Distributed loads can be entered in the Loadcase window in the aft limit and forward limit cells. Moment columns (mass * lever) can be displayed if desired. The aft limit and forward limit columns only appear when Longitudinal Strength analysis is selected and the distributed loads will only have an effect on the results in this analysis mode.Chapter 3 Using Hydromax
The Relative density and Fluid Type which allow you to override the default tank densities as defined for each tank in the Compartment Definition window.

Trapezium shaped distributed load. they will be automatically included in the loadcases (but not in Loadgroups which do not contain tanks). Red = Green divided within middle 1/3 of centre. the centre of gravity should lie within the middle third between the forward and aft limits of the load. but within the middle third 1/3 of the centre. at these extrema. the load distribution becomes triangular.
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. Tanks will be automatically treated as distributed loads for the longitudinal strength calculations.
Note: Since the load is distributed as a trapezium.Chapter 3 Using Hydromax
Evenly distributed loads.
Tank Loads
When you create tanks using the compartment definition. Red = green and divided in the centre.
For trapezium shaped distributed loads the centre of gravity is not midway between the boundaries.

It also means that this lightship mass distribution would only need to be defined and edited in one location instead of in each loadcase.
Updating tank values in the loadcase
Irrespective of whether you have updated the values in the Loadcase Condition.
For the example above this means that the lightship mass distribution would be defined as a Loadgroup and then this Loadgroup could be referenced in any number of loadcases. we have defined the following rules:
A special type of Loadcase called a Loadgroup has been defined.
When a tank is changed in the Compartment definition table. Also see: Update Loadcase on page 206
Loadcase cross-referencing. the Loadcase will be automatically updated as the first step of any analysis using the Loadcase information. A Loadcase can reference any number of Loadgroups A Loadgroup is referenced in a Loadcase by typing the name of the Loadgroup to be referenced in the Item column You can factor the referenced Loadgroup by changing the value of the Quantity column in the Loadcase. To prevent the problems of recursively including the same loadcase and also prevent tanks from being included more than once. Loadgroups
It is possible to cross-reference one loadcase from another. A Loadgroup does not contain tanks Only a Loadgroup can be referenced Only a Loadcase can reference a Loadgroup. Loadgroups may be analysed in the same way as Loadcases – but remember the tanks are implicitly empty in a Loadgroup. a sounding or a weight. select Update Loadcase from the Analysis menu or toolbar. question marks may be shown in the loadcase momentarily while the tank‟s new volumetric properties are being calculated. Tank level can be given as either a percentage of full capacity. The Loadcase properties dialog (Case menu) is used to define a loadcase as a Loadgroup:
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. volume.
The tank Unit Mass is the tanks mass at 100% filling. This is useful if you wish to define a detailed lightship mass distribution but do not want to have it displayed in full in each loadcase.Chapter 3 Using Hydromax
Tanks have a quantity value. To update the loadcase for changes in tank loads. expressed as a percentage of the full capacity and a weight column.

The Lightship load group can then be cross-referenced into any loadcase
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.Chapter 3 Using Hydromax
This lightship Loadgroup contains the lightship mass distribution along the ship.

By default use tank defined densities:
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. This allows you to load the same tanks with different fluids in different Loadcases – as might be the case for a product carrier.
Loadcase density override
It is now possible to override the default tank fluid densities as defined in the Compartment definition window.Chapter 3 Using Hydromax
The referenced Loadgroup is automatically calculated and the appropriate values included in the Loadcase:
Note: Loadgroup naming The cross-referencing of loadgroups in a loadcase is case insensitive. for instance.

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.0) specific gravity and it will override the tank value:
Type in any string that doesn‟t begin with an “L” for the fluid and it will revert back to the tank value:
Type in some thing that begins with an “L” and it will revert back to the “Private” density of the loadcase item.Chapter 3 Using Hydromax
Type in a valid (>0.

This method approximates the movement of fluid due to heeling and is based on the fluid shift in a 50% full rectangular.(69) Ch 3. User specified A user specified value is used for all levels and heel angles. The options available are Maximum Hydromax will use the maximum free surface moment of the tank in upright condition for all fluid levels. making the tanks‟ free-surface parallel to the sea surface. the Loadcase will sum the free surface moments.3 for the calculation of the free surface moment. This can be loaded into Hydromax and referenced in any Loadcase. Besides a general explanation on how to model tanks using the compartment definition table. box-shaped-tank. Hydromax calculates the actual position of the fluid in the tanks taking into account heel and trim. Fluid simulation If the Fluid simulation option is selected in the analysis menu.
Modelling Compartments
This section will describe in detail how to model different types of tanks and compartments. thus the actual vessel CG is recalculated accounting exactly for the static shift of the fluids in slack tanks. it is possible to choose the type of free surface moment to be applied for each tank in a Hydromax Loadcase. Actual Hydromax uses the free surface moment for the current fluid level of the tank in upright condition.htk) 
Select the Compartment Definition table by clicking on the Compartment Definition tab at the bottom of the Input window. no correction is made to the upright VCG.Chapter 3 Using Hydromax
Free surface correction
If the corrected VCG fluid option has been chosen. For other shapes and fillings of tanks it will not correctly approximate the free surface moment. Instead. When the corrected VCG method is selected in the analysis menu. Select New Compartment Definition from the File menu

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.
Workshop structure
Workshop can save a Loadgroup that contains the masses of all the structural parts. this section contains a number of important sections that the user should be aware off when modelling tanks:
Number of Sections in Tanks on page 67 Tank and Compartment Permeability on page 59
Creating a Compartment definition file (. divide by the total displacement to obtain the VCG correction and adjust the VCG accordingly to obtain the corrected fluid VCG. IMO Hydromax uses IMO MSC75. at every step of the analysis.

The 'F' and 'A' abbreviations stand for Forward and Aft. in other words the two ends of the compartment.
Add will add a tank after the currently selected compartment and Delete will delete the currently selected compartment(s). The accelerator keys Ctrl+A and the Delete key may also be used to add and delete entries respectively. Hydromax will form the sections that define the tanks and compartments.
Adding and Deleting Compartments
Before you can start adding compartments. or an analysis started. resulting in a parallel tank.Chapter 3 Using Hydromax
This will give you a new set of compartment definitions with one default tank. Each value defines one of the six planes of the tank. the top and bottom. This box will be called the Boundary Box. When the “Update Loadcase” command from the Analysis menu is used. The boundary box is made up of the fore and aft extremities of the tank. The column headings in the Compartment Definition table include terms such as 'F Bottom.
Modelling Box Shape Tanks
Simple tanks and compartments are created by specifying six values that define a boxshaped boundary for the tank. Compartments may be added or deleted by

Select Add or Delete Compartment from the Edit menu. make sure you have created a Compartment definition file. This is done by finding the intersection of the tank bounding box and the hull. This means that the value is identical at the aft end of the tank to the forward end. and the port and starboard limits of the tank. 'A Top'. 'F Port' and 'A Starboard'.
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.
See Longitudinal Extents of Boundary Box on page 67 for some recommendations regarding setting the boundary box. see above. You will notice that aft columns contain the word "ditto".
Box shaped compartments can be formed from the numerical values in the compartment definition table. Thus it is not necessary to make the tanks fit the hull manually – this is done automatically by Hydromax.

Chapter 3 Using Hydromax

Modelling Tapered Tanks

The default is for compartments to have parallel sides. If you wish to define tapered compartments, it is possible to enter different transverse and vertical values for the points defining the forward and aft ends of the compartment. If a different value is entered in one of the “ditto” columns, a tapered tank will result. Tanks can be tapered or sloped in Plan or Profile views. Hydromax does not have a mechanism for creating a sloped tank boundary in the Body Plan view.

By changing the “ditto”-input fields, tapered tanks can be formed

Note: Tapering can be done in Plan and in Profile view. Tapered tanks in Body Plan view have to be created using a boundary surface. See Modelling Tanks Using Boundary Surfaces on page 54.
Linked Tanks

Tanks and compartments may be linked. This means that although they are defined as separate tanks, they act as a single tank with a common free surface. To link tanks, compartments or non-buoyant volumes, first make them the same type as the parent and give them the same name. The easiest way to do this is to copy and paste the name from the Name column of the parent row into the Name column of the linked tank row. They may then be linked to the parent by typing l or linked in the Type column. Linked tanks and compartments do not have to be physically linked in space. However, the fluid in a linked tank or damaged compartment is always assumed to be able to flow freely between the linked volumes.

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Chapter 3 Using Hydromax

Modelling Tanks Using Boundary Surfaces

Tanks, compartments and non-buoyant volumes may have their boundaries defined by surfaces as well as being constrained to particular dimensions. This allows for the modelling of arbitrarily shaped tanks.

Forming tanks using boundary surfaces

The surfaces to be used to define the tank boundaries are selected by clicking in the Boundary Surfaces column in the middle of the Compartments Definition table. A dialog will appear that allows you to select which surfaces form the boundary of the tank. If a tank uses boundary surfaces, the cell in the Boundary Surfaces column is coloured blue.

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Chapter 3 Using Hydromax

If you wish to use a Maxsurf surface to define a tank or compartment, tick next to the surface name in the Boundary Surface list. Note that symmetrical surfaces appear twice as there will be a starboard and a port side copy of the surface. The Starboard surface is first in the list and the Port surface second. The port surface is also identified with the suffix (P) after the name. Note: Only internal structure surfaces appear in the boundary surfaces list. Symmetrical surfaces are duplicated, with the port-side surface having “(P)” appended to the surface name. After selecting the internal surfaces, it is necessary to type in the extents of the boundary box. Hydromax will automatically set the “Fore” and “Aft” limits of the boundary box to just within the longitudinal limits of the Boundary Surface. This ensures that at least 12 sections are inserted in the tank. Also see: Forming Compartments on page 62 Number of Sections in Tanks on page 67 Longitudinal Extents of Boundary Box on page 67
Modelling External Tanks

External tanks may not be modelled in Hydromax. However, it is normally possible to add "Hull" surfaces in the Maxsurf model, which will enclose the external tanks. The tanks can then be modelled in Hydromax.

Additional box-shaped hull surfaces used to define deck tanks

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Chapter 3 Using Hydromax

Modelling Non-Buoyant Volumes

Non-buoyant volumes are effectively permanently flooded compartments. These parts of the hull can normally be modelled using trimmed hull surfaces. However, there are occasions where it is more convenient to use non-buoyant volumes. In some cases, where the volume to be flooded forms sections within the hydrostatic section, this is the only option, e.g. waterjet ducts. The choice whether to use trimmed surfaces or nonbuoyant volumes is primarily determined by the length of the non-buoyant volume relative to the length of the vessel. Using trimmed hull surfaces When the length of the non-buoyant volume, relative to the length of the model, is large enough; the non-buoyant volume can be calculated accurately from the hull sections. If possible, trimmed surfaces should be used. The picture below is a good example of when to use trimmed surfaces.

Propeller tunnels modelled with trimming surfaces

Using tank type: Non-buoyant volume In some cases using trimmed surfaces is just not possible. For example, when the sections of the non-buoyant volume are entirely enclosed within the hull sections (as is the case for a water jet duct) the use of a non-buoyant volume is the only way in which these features can be modelled.

Water-jet ducts modelled as non-buoyant volumes

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Chapter 3 Using Hydromax

Another occasion when non-buoyant volumes should be used, is when the length of the compartment relative to the length of the hull is too small to calculate its volume from the hull sections. A good example of this is a bow thruster on a long ship. If the vessel is very long, and the thruster duct is of small diameter, there may not be sufficient sections to model it accurately (even if you use the maximum of 200 sections for the Hydromax model). In this case you are better off modelling the thruster duct as internal structure and using these surfaces to define a non-buoyant volume. For example: in the image below the bow thruster volume is only calculated with one section.

For more information, see Number of Sections in Tanks on page 67. Tip: Besides increasing the number of sections through the bow thruster from 1 to 12, modelling the thruster duct as a non-buoyant volume has the additional advantage of being able to specify a Tank and Compartment Permeability, and hence also account for the thruster.

When a tank is defined within a compartment, Hydromax will automatically deduct the volume of the tank from the compartment volume using a “linked neg. (negative) compartment”. This is necessary for damage cases where the compartment is flooded and the volume of the tank should be treated completely separately from the compartment. Linked negative compartments are deleted and recreated whenever a tank or compartment is added, deleted or modified. Negatively linked compartments are displayed on the bottom of the Compartment Definition table solely for reference purposes and are not under direct user control. This means that linked negative compartments cannot be added, deleted or modified.
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Chapter 3 Using Hydromax

Linked negative compartments are named based on both the parent compartment as well as the tank from which the linked negative compartment was derived. For example a linked negative compartment might be named “Compartment3 (Stbd Hydr Oil)” to reflect that it is derived from the intersection of Compartment3 with the Stbd Hydr Oil tank.
Tanks Overlapping

As mentioned earlier in this manual, only compartments and non buoyant volumes or tanks can overlap with each other. Tanks or compartments of the same type (eg two tanks) can not overlap. A tank and a non-buoyant volume are also not allowed to overlap. Hydromax will first try to form tank sections and then check whether these sections overlap tank sections of adjacent tanks. When two conflicting or overlapping tanks or compartments are detected during the forming process, you will receive an error message:

Notice that the compartment definition row number of the tank is given in brackets i.e. tank #8 intersects tank #3.

Troubleshooting Overlapping Tanks Sometimes the reason for the conflict can be quite simple: eg an overlapping boundary box. However, when you are modelling tanks using boundary surfaces, the surface boundaries act as a boundary between two adjacent tanks and the bounding box extents are allowed to overlap. In these cases, it can be quite difficult to see why the tanks overlap, especially if you have a large number of tanks already defined.

By temporarily deleting all tanks except for the one that does not form, it often becomes clear why the tank overlaps. In the case of the image above, the tank‟s fwd most section goes all the way to the CL (probably because the fwd boundary box extent is just fwd of the boundary surfaces or exactly on the edge of a boundary surface). This causes this particular tank to “overlap” with surrounding tanks.
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and an upper engine room compartment. Depending on the level of accuracy required.
Now that you know how to fix it. and the other when it is damaged. the permeability fraction is also applied to the free-surface-moment contribution of that tank or compartment.. The lower compartment will have a permeability of. In the case of damaged tanks and compartments. for example. Do NOT save!! Open saved Comp def file Fix compartment. compartments typically have structure (other than plate stiffeners) and equipment inside. Save & move on to next compartment. which is used when the tank is intact. 60% and the upper compartment a permeability of 95%. the engines and equipment could also be modelled individually as empty tanks. The compartment permeability is applied when the compartment is flooded in a damage condition and the non-buoyant volume permeability is applied at all times since it is always flooded. Compartments and non-buoyant volumes have only one permeability. For example an engine room with engines and auxiliaries at the tanktop could be divided up in a lower. In case of large variations in permeability within a compartment it is recommended to model separate linked compartments with separate permeability to increase accuracy.
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. thought it is listed in both columns. one.
Relative Density of Tank Fluids
Relative Density (Specific Gravity) values can be typed directly into the Relative Density column of the Compartment Definition table. Permeability of Compartments As opposed to tanks. inspect tank sections Try to fix tank definition. eg by selecting additional boundary surfaces Close comp def file.Chapter 3 Using Hydromax
Procedure to Fix Overlapping Tanks:
     
Save Model Go into Comp def window Save comp def Delete all tanks except for one you wish to investigate form tanks.
   
Tank and Compartment Permeability
Tanks may have two permeabilities.

so it is normally only necessary to type the first few letter of the name). or if you prefer. either as the name or as one of the single letter codes (when entering the name. all entries for that fluid in the compartment definition are automatically updated.
Compartment and Tank Ordering
The tank definition order can be adjusted in a similar way to loads in the loadcase. If a fluid type is entered. the relative density value is obtained from the value specified in the Density dialog. it is often useful to check individual tanks. Whenever values are changed in the Density dialog (see Density of Fluids on page 150). Groups of linked tanks and compartments will be moved together.Chapter 3 Using Hydromax
Alternatively the fluid type can be entered into the Fluid Type column. hence you should design these surfaces to the inside of the tank. auto complete is used. selected tanks may be displayed in the following manner:
 
Define a damage case Select only damaged tanks and compartments for display.
Assembly view can be used to show and hide tanks/compartments
Using damage cases. If the tank defines a cargo tank that will carry different liquid cargoes. You can either control the tank visibility through the Assembly window. you can use damage cases to quickly change the display to show certain tanks. turn off the display of intact tanks and compartments. Select the rows you wish to use and use the Edit | Move Items Up or Down commands (there is no provision for sorting tanks alphabetically).
Tanks and Surface Thickness
If you have specified that Hydromax should include the surface thickness. the tanks. compartments and non-buoyant volumes will correctly account for the surface thickness and its projection direction: the tanks will go to the inside of the hull shell.
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. the default density specified here in the compartment definition may be overridden in the loadcases.
Compartment and Tank Visibility
When creating complicated tank plans. Note: Thickness of boundary surfaces are not taken into account.

Only tank sections that lie on or near the current station are shown – this makes it easier to verify that the tanks have been formed.Chapter 3 Using Hydromax

Select whether you want to see the tank outline or the tank sections (tanks sections are preferable when checking that tanks have been formed correctly since it is these sections which are used to determine the tank volume and other properties). Use this to quickly turn tanks on and off by changing their damage status. tank sections are also displayed in the Bodyplan view when the “Show single section” option is selected. Choose the damage case from the Analysis toolbar Set any of the tanks and compartments you wish to be visible to damaged in the damage case window.
 
You can make the damage case window quite small and tile it next to the perspective view.
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.
Using a damage case to quickly change the tank and compartment visibility
Tank sections
When in Tank Calibration mode.

Chapter 3 Using Hydromax
Forming Compartments
Tanks and compartments are formed automatically by Hydromax (once the tank extents and any boundary surfaces have been defined) by selecting Recalculate Tanks and Compartments from the Analysis menu.
Hydromax uses three input items to form the compartment
Boundary surfaces (if defined) Boundary box Hydromax Hull sections
Starting position The starboard tank margin plate is modelled using an Internal Structure surface from Maxsurf. First a step-by-step outline of the tank forming process is given. the starboard waterballast tank below will be created using boundary surfaces. Understanding these processes may assist you in rare situations where the tank forming does not work as expected.
An example of a port and starboard waterballast tank with a pipe tunnel at the centreline. The water ballast tanks have a margin plate on the side. This section describes the internal tank-forming process that Hydromax uses to form tanks. The formed status of a tank (yes or no) is shown in the last column of the compartment definition table. followed by the tank section insertion process.
Starting point: Hydromax Hull sections with an internal surface and a bounding box
Also see: Modelling Tanks Using Boundary Surfaces on page 54 and the Maxsurf manual on internal structure surfaces
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.
Step-by-Step Tank Forming Process
As an example.

Make sure that the boundary surfaces:
Form a closed section contour.Chapter 3 Using Hydromax
Step 1: Close Internal Structure Surface
Hydromax will close the Internal Structure Surface contour by drawing a straight line between the ends of the opening. Hydromax will use the trimmed internal structure surface. As with the hull sections. Usually the internal structure surfaces are best to be left untrimmed. Another common cause of unexpected results is trimming. Step 2: Clip to Boundary Surface Using the closed surface section contour Hydromax can now form a closed compartment section. The area inside the selected surfaces will define the tank contour.
Hydromax uses the same method for forming the tank section from the boundary surfaces as for forming the hydrostatic sections through the hull. the surfaces selected to form the tank boundary must form closed section contours at all longitudinal positions through the tank. or There is no more than one opening – the opening will be closed with a straight line
Note: Hydromax will close the section contour of the selected boundary surfaces only. The tank or compartment looks like this at this stage:
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. If you selected “use trimmed surfaces” while opening the Maxsurf model. Often a tank is not formed as expected because only one side of the internal structure surface was selected for example the portside (p).

Chapter 3 Using Hydromax
Step 3: Clip to Hull Hydromax will clip the compartment section to the hull. In practice additional surfaces would be required. The boundary box is formed from the numerical input in the Compartment definition table. A more realistic example is shown in the following section.
Step 4: Clip to Boundary Box Finally the compartment section is clipped to the boundary box.
More realistic surface-bounded tanks
Whilst the above example shows the principles by which surface-bounded tanks are formed. it is not really realistic because it would not be possible to define a tank above the surface-bounded double bottom tanks. In this example the vessel has both wing and double bottom tanks with non-rectangular cross-sections thus requiring them to be defined by boundary surfaces – see blow:
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.

Hydromax will normally place twelve sections between the forward and aft limits defining the tank. If this results in a section spacing greater than the spacing for the hull spacing. additional sections will be inserted into the tank so that the tank section spacing match the hull section spacing. Also see Longitudinal Extents of Boundary Box on page 67
Longitudinal Extents of Boundary Box
For tanks near the ship‟s extremities it is good practise to set the “Fore” and “Aft” limits in the compartment table to just inside the hull surface (say 1mm). In most cases.Chapter 3 Using Hydromax
Surfaces for double bottom tanks
Surfaces for wing tanks (top is closed automatically)
Number of Sections in Tanks
The volume of a tank or compartments is calculated by integrating section properties along the length of the tank. The following example illustrates why:
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. Thus it is important to have a sufficiently large number of sections to accurately model the tank. this will be done automatically by Hydromax.

Also see Number of Sections in Tanks on page 67 Forming Compartments on page 62
Compartment Types
Five compartment types can be created using the Compartment Definition table . they should be set to just inside the extents of the hull surfaces to ensure that at least 12 sections are used to calculate the tank volumes. linked tanks. For internal structure surfaces that are used as boundary surface. linked compartments and non-buoyant volumes.
But if the boundary box is set just inside the forward limit of the bulbous bow:
To recap – Near the ship‟s extremities. Note that transversely and vertically there are no such restrictions. compartments. the longitudinal extents should not be set to extreme values.tanks. Hydromax will automatically set the “Fore” and “Aft” limits of the boundary box to just within the longitudinal limits of the boundary surface.Chapter 3 Using Hydromax
If the boundary box is set like this:
The number of hull sections is dependent on the section spacing in the model.
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. This ensures that at least 12 sections are inserted in the tank.

Chapter 3 Using Hydromax
Tanks Will be included in the tank calibration output and are automatically added to the loadcase. shown below. or Analysis | Update Loadcase. any tank that it is linked to will also be regarded as damaged. or using one of the following commands: Analysis | Recalculate Tanks and Compartments. Tanks need not be adjoining to be linked. Non-Buoyant Volumes Are only used to specify compartments of the vessel which are permanently flooded up to the static waterline. any changes to the sounding pipe due to tank geometry changes will also have to be made manually. they can be remote from one another. Linked Compartments Work in the same way as linked tanks.
Sounding Pipes
Hydromax allows sounding pipes to be defined for each tank. moon pools. One sounding pipe per tank is permitted and up to nine vertices per sounding pipe. and essentially behave as damaged compartments. Linked Tanks Will have their volume added to the parent tank with the same tank name.
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. Automatically created sounding pipes will be recalculated if the tank geometry changes.
Edit Sounding Pipes
To customise a sounding pipe. allowing inclined. Hydromax creates a default sounding pipe when the tank is formed (either by running an analysis. If the lowest point of the tank is shared between several locations (e. To change the type of a tank. In this case the tank linking simulates tanks with cross connections. The default sounding pipe is placed at the longitudinal and transverse position of the lowest point of the tank. However. bent or curved sounding pipes to be modelled. They are not included in the tank calibration output and will not be added to the loadcase. once the sounding pipe has been edited manually. type the first character of the tank type (t. They are ideal for defining water-jet ducts. if a tank is damaged. They are not included in the tank calibration output and will not be added to the loadcase. They do not have a separate entry in the loadcase. etc. Compartments Are only used to specify compartmentation for damage. the bottom of the tank is flat either longitudinally or transversely) the default sounding pipe location is placed at the aft-most low point and as close to the centreline as possible. The top of the sounding pipe is taken to be level with the highest point of the tank and the default sounding pipe is assumed to be straight and vertical. c or n) in the Type column of the Compartment Definition table and then press Enter. This allows you to damage a complex compartment configuration by linking compartments together and damaging the parent compartment. you need to use the Sounding Pipes table in the Input window.g. In addition. This will automatically set the tank/compartment to the correct type.

by clicking on the tabs at the bottom of the Input window. Hydromax uses its default value based on a reasonable division of the depth of the tank.Chapter 3 Using Hydromax
You can activate this window by selecting from the Windows | Input | Sounding Pipes menu.e. To add vertices to create a bent sounding pipe. or by clicking on the icon in the window toolbar. This is done by specifying a numerical value for the increment for each tank in the Calibration Spacing column of the Sounding Pipes Input window.
If no increment is entered. then click on the first row of a particular sounding pipe and choose Edit | Add or use the Ctrl+A key combination.

Type the value of the desired calibration increment in the Calibration Spacing cell for the tank calibration you wish to modify. Unwanted vertices can be deleted by clicking on the relevant row in the table and selecting Edit | Delete or by hitting the Delete key. A new row will be added to the sounding pipe and the longitudinal position.
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. it is not acceptable to have S-bends in the sounding pipes. In this case the Sounding Pipes table will display “Auto” in the Calibration Increment column for the tank. Note that each successive vertex in a sounding pipe must be no higher than the previous vertex i. offset and height of the vertex can be edited.
Calibration Increment
Hydromax allows user definable increments (or: intervals) for tank soundings. make the sounding pipe type User Defined.

Damage Case Definition
In all but the floodable length and tank calibration analysis modes. Hydromax is capable of including the effects of user-defined damage.
Adding a Damage Case
To add a damage case. make the Damage window active and select Add Damage Case from the Case menu. Note that it is not possible to delete the intact case. select the intact case column. to insert a damage case immediately after the intact case. Volumes that are permanently flooded should be defined as non-buoyant volumes. simply select the columns to be deleted in the Damage Window and select Delete Damage Case from the Case menu. soundings will step evenly along the inclined length of the sounding pipe.
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. Several damage cases may be added in one go by selecting a number of columns.
Renaming a Damage Case
The name of the current damage case may be changed by selecting Edit Damage Case when the damage case window is active. the current damage case is selected from the Analysis toolbar – see below. If the sounding pipe is inclined or if it has multiple angles. not along the vertical axis of the tank. The new damage case is added after the currently selected damage case column. You may specify a name for the Damage Case in the dialog.
Deleting a Damage Case
To delete damage cases. Hydromax allows the user to set up a number of damage cases.Chapter 3 Using Hydromax
Note Increments are measured along the sounding pipe. Each new damage case will have a column in the Damage Window and a tick may be placed to indicate which tanks and compartments are damaged for that particular Damage Case.

their weights and levers are no longer displayed in the Loadcase window and the word „Damage‟ is displayed in the quantity column. To perform analyses for the intact vessel. all damaged tanks and compartments will be displayed in damaged tank or damaged compartment colour respectively. you should toggle the damage status of the damaged tanks.
Displaying Damage Cases
When a damage case is selected. This is because Hydromax uses the “Lost buoyancy” method rather than “Added mass”. This is also the case for the Floodable Length analysis which effectively sets up its own longitudinal extent of damage. turning off all damage in all the damage cases (use the fill down command) and then pasting back in the original data from where it was stored in the spreadsheet. Note: Hydromax uses the “Lost buoyancy” method rather than “Added mass”.
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. Hydromax assumes that all compartment definition has been done after the tanks have been defined. select Intact as the current damage case.
The Loadcase and View windows will reflect the damage defined in the current damage case. If you have linked tanks or compartments or added tanks within compartments after the definition of a damage case. Note that carrying out a Tank Calibration analysis will force the intact case to be selected. Flooding is considered to be instantaneous up to sea level. Any subsequent analyses will take into account the damaged compartments. Any tank fluids are treated as having been completely replaced by seawater up to the equilibrium waterline.Chapter 3 Using Hydromax
Selecting a Damage Case
The current damage case is selected from the Analysis toolbar. These colours can be specified in the View | Colours and lines menu. When tanks have been damaged. This is simply done by copying all the damage case data to a spread sheet. In the Loadcase Window damaged tanks are displayed with the label 'Damaged' in the Quantity column. and all values set to zero.

Extent of Damage Cases
The damaged compartments can automatically be set by using the Case | Extent of damage command.Chapter 3 Using Hydromax
The Loadcase Window displays damaged tanks and excludes them from any calculations. Select the column of the damage case you wish to specify the extent of damage for and choose Extent of Damage from the case menu:
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Chapter 3 Using Hydromax
Defining the damaged compartments by specify the extent of damage. There are several types of Key Points:
Down Flooding points Potential Down flooding points Embarkation points Immersion Points
Only downflooding points are used in determining the downflooding angle. Immersed key points will be displayed in the same colour as flooded tanks or compartments. A new point will be inserted below the currently selected row in the table. You will be given a default point. Vessels which have symmetrical key points on starboard and port sides must have both key points added to the table.
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.
Adding Key Points
To start adding downflooding points go to the Key Points table. click anywhere in the row of the point to be deleted and select Delete. which is used in criteria evaluation. select New Key Points from the File menu.g. a positive offset is to starboard and a negative offset is to port.
Specify the extent of the damage – any tanks or compartments that lie partially or wholly within the extent of damage will be automatically flagged as damaged:
Automatically generated damage case from using Extent of Damage command.
Key Points (e. Key points may be placed asymmetrically. To delete more than one point at a time.
Deleting Key Points
To delete a Key point. The other types of points have their freeboard measured but are not used for the evaluation of the downflooding angle and are for information only. choose Add from the Edit menu or press Ctrl+A. Down Flooding Points)
Key points such as downflooding points and hatch openings can be defined in Hydromax using the Key Points window. The points may be displayed in the Design View window and will be displayed in different colours depending on whether or not they are immersed. click and drag over the rows you want deleted. To add additional key points to the table.

and a height.
Editing Key Points
Key points are defined by entering a name. Select the tank or compartment from the combo-box in the Linked to column of the Down Flooding Points table in the Input window:
Downflooding points that are linked to tanks or compartments. Click in any cell and enter the name or value you require. a longitudinal position. which are damaged in the currently selected damage case. The type of Key Point may be selected from the combo-box in the Type column of the Down Flooding Points table in the Input window:
Links to Tanks or Compartments
Downflooding points may be linked to tanks or compartments. These downflooding points will appear italicised and an asterisk (*) is postfixed to the downflooding point‟s name in the DF Angles table of the Results window:
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. a transverse offset from the centreline.Chapter 3 Using Hydromax
Select Delete from the Edit menu. and the selected rows will be deleted. will be ignored when computing the downflooding angle. All points are entered relative to the zero point.

the freeboards after an Equilibrium or Specified Condition analysis. Hydromax automatically calculates the position of the margin line 76mm below the deck edge when the hull is first read in. The modulus value is not currently used as deflections are not calculated. Note: Linking a downflooding point to a tank does not mean that Hydromax will consider a tank damaged when the downflooding point is submerged.Chapter 3 Using Hydromax
The downflooding angles for each of the points are displayed in the results window.
Modulus Points and Allowable Shears and Moments
The Modulus window can be used to enter maximum allowable shear forces and bending moments for each section. Immersed points are highlighted in red in the Freeboard column.
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. immersion angles or freeboards (depending on the analysis) are also given for the margin line and deck edge. One or more points can be entered in this window. Asymmetric margin lines and deck edges are not supported. In addition to the Key Points results. If necessary. Once this has been done for all the points that need to be changed. ensuring that the margin line follows the hull shape precisely. It is only necessary to modify the height value of the margin line points.
Margin Line Points
The margin line is used in a number of the criteria. selecting Snap Margin Line to Hull in the Analysis menu will project all of the points horizontally onto the hull surface. Points may be added or deleted as required using the procedure described in Adding Key Points and Deleting Key Points on page 74. The downflooding angles are computed during a large angle stability analysis. In the Name column the longitudinal position where immersion first takes place (or the lowest freeboard) is given. the points on the margin line may be edited manually in the Margin Line Points window (the deck edge is automatically updated so that it is kept 76mm above the margin line). Allowable shear force and/or bending moment can be specified at each point. This form of automatic flooding is not supported in Hydromax yet.

Please refer to Chapter 4 Stability Criteria starting at page 163 for information on defining and selecting criteria. The following analysis types are available in Hydromax:
Upright Hydrostatics Large Angle Stability Equilibrium Analysis Specified Conditions KN Values Analysis Limiting KG Floodable Length Longitudinal Strength Tank Calibrations MARPOL Oil Outflow Probabilistic Damage
Also. Stability criteria are required to perform a limiting KG and Floodable Length analysis. Points may be added or deleted as required using the procedure described for the key points.
Floodable Length Bulkheads
Bulkheads entered in the Input window are used for Floodable Length analysis in order to optionally plot the compartment lengths in the floodable length graph for easy verification that the critical compartment lengths are not exceeded.
Analysis Types
After specifying the input values and checking the Hydromax model.Chapter 3 Using Hydromax
To start a table of allowable shear forces and bending moments. In this section the different analysis types available in Hydromax will be described.
Stability Criteria
Stability criteria may be evaluated after a Large Angle Stability analysis and after an Equilibrium analysis. The allowable values can be saved and recalled as text files by using Open and Save from the File menu. For more information see Floodable Length on page 102. New allowable values can be inserted by selecting Add from the Edit menu and entering a longitudinal position as well as an allowable shear and/or moment. the analysis can be performed. bring the Modulus table to the front and choose New Modulus Points from the File menu with the Modulus window frontmost. some general information is given on:
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. The Bulkheads are automatically sorted by longitudinal position. These allowable values are displayed as lines on the longitudinal strength graph.

specify range of drafts for analysis Trim from the Analysis menu.
Choosing Upright Hydrostatics
Select Upright Hydrostatics from the Analysis Type option in the Analysis menu or toolbar.
Upright Hydrostatic Analysis Settings
The following analysis settings apply for Upright Hydrostatic Analysis:
Draft from the Analysis menu. one or more graphs may be shown – select the graph to be displayed from the pull-down menu in the Graph window. Following each analysis.Chapter 3 Using Hydromax
Starting and Stopping Analyses Batch Analysis
The required analysis settings and environment options will be discussed separately and in more detail in the next two sections of this chapter. at zero or other fixed trim.
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. you may specify a fixed trim for all drafts
A range of drafts for upright hydrostatic calculations can be specified using the Drafts command from the Analysis menu. the available options depends on the current results table or graph:
Data format dialog for Upright hydrostatics table and graph
Upright Hydrostatics
Upright hydrostatics lets you determine the hydrostatic parameters of the hull at a range of drafts. The Data Format dialog can be used to specify what is displayed in some graphs and tables.

The Vertical Centre of Gravity is also required for the calculation of GM etc (if the vessel is trimmed. together with the number of drafts to be used. the LCG also affects these measurements).
Upright Hydrostatics Environment Options
The following environments can be applied to the upright hydrostatics analysis:
Density from the Analysis menu Wave Form (if any) Damage (or Intact) from the Analysis toolbar
Upright Hydrostatic Results
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.Chapter 3 Using Hydromax
Initial and final drafts can be entered. the initial draft defaults to the draft at the DWL in Maxsurf. When a design is first opened. Similarly the VCG defaults to the height of the DWL.

to ensure accurate evaluation of the criteria. select range for analysis Trim (fixed or free) from the Analysis menu
If criteria are being evaluated.
Choosing Large Angle Stability
Select Large Angle Stability from the Analysis menu or toolbar.
Large Angle Stability
Large angle stability lets you determine the hydrostatic parameters of the hull at a range of heel angles either with or without trim or free-to-trim.Chapter 3 Using Hydromax
The curves of form are shown on a separate graph and the sectional area may be show for any of the drafts: see Select View from Analysis Data on page 159.
Large Angle Stability Settings
The following analysis settings apply for Large Angle Stability Analysis:
Displacement and Centre of Gravity using the Loadcase window Heel from the Analysis menu. the heel range and heel angle steps should be chosen accordingly.
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you can enter negative values and test full 360 degrees of stability if you wish.Chapter 3 Using Hydromax
Note You can select positive heel direction (port or starboard). safe steady heel angle Stability Criteria evaluation Downflooding angles to key points. Also see: Heel on page 141 in the Analysis Settings section. The criteria are only evaluated on the side of the graph that corresponds to positive heel angles. the one that would be reported in the criteria would be the one with a positive heel angle (even if the one at negative heel occurred at an angle closer to zero).
Large Angle Stability Environment Options
The following environments can be applied to the large angle stability analysis:
Fluid simulation of tank fluids centre of gravity Density Wave Form (if any) Damage (or Intact) from the Analysis toolbar Stability Criteria
Large Angle Stability Results
Large Angle Stability Analysis results are:
Hydrostatic data table for each angle of heel GZ curve Dynamic stability (GZ area) curve Graph of hydrostatic parameters against heel angle Graph of max. deck edge and margin line Curve of areas at each heel angle
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. For example: when using a -180 to 180 heel range. However. Some criteria require calculations of GZ at negative heel. the results may be two angles of vanishing stability.

Chapter 3 Using Hydromax
Dynamic stability Graph A graph of the GZ area integrated from upright may be plotted. Curves of Form. you can display the maximum safe heeling angle curves by selecting the graph type in the pull-down menu. Curve of Areas Shows the curve of areas for the currently selected heel angle (use Display | Select view from data to chose the heel angle from the GZ results table).
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. Once a GZ curve has been calculated. for example the angle of downflooding or angle of deck edge immersion. Large Angle stability Graph. Shows the variation of hydrodynamic properties with heel angle. Graph of maximum safe steady heeling angles for sailing vessels These calculations are derived from the value of GZ at a critical heel angle. features such as downflooding angle are also included on the graph.

Chapter 3 Using Hydromax
The parameters for the calculation can be modified in the Display | Data Format dialog (this graph must be selected in the topmost window):
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.

You can also change the shape of the heeling arm curve and the gust ratio. This will give you the same result as for the gust limiting line.
The first part of the dialog is almost exactly the same as the “Angle of equilibrium . 45 and 60kts.
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. you can specify the squall wind speeds (you can add any number) The default gives three wind speeds of 30.derived wind heeling arm” criterion. This allows you to specify the critical condition that should not be exceeded due to a gust or squall. MCA require downflooding but you can include additional criteria if desired. In the lower-left. Finally you can adjust the axis limits. This is because normally you will have computed a GZ curve for a wider heel range than you would wish to display in this graph – it is uncommon to sail a vessel with a steady heel angle of greater than 40 degrees.Chapter 3 Using Hydromax
Analysis options for the calculation of Maximum steady heel angles (Display | Data Format). It can often be useful to duplicate this criterion in the GZ criteria that are evaluated.

especially at the lower heel angles – typically steps of 1degree. the most common reason for this is that the GZ curve has not been calculated up to a sufficiently high angle of heel and downflooding angle cannot be found.
To obtain smooth curves. it may not be possible to evaluate the curves. Full details of the calculations can be found in:
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.Chapter 3 Using Hydromax
The same safe angle of heel to prevent downflooding in the event of a gust (16. the GZ curve should be calculated at small intervals of heel. Under some circumstances.5 deg) is found.

www. see: Important note: heeling arm criteria dependent on displacement on page 240.uk Stability Criteria Evaluation The criteria results are displayed in the Criteria tab in the results window. please refer to the Results Window on page 185 in the reference section. A downflooding angle of zero degrees indicates that the key point is immersed at zero degrees of heel.
Downflooding points that are linked to tanks or compartments that are damaged in the currently selected damage case. Important: For important information on varying displacement while evaluating criteria. ed.mcga. the large angle stability analysis should be carried out heeling both to starboard and to port. For the margin line and deck edge the longitudinal position at which immersion first occurred is provided. For more information on how to customize the display of the criteria results. the Key Points Data table lists the downflooding angles of the margin line. Only the positive downflooding angles are displayed. hence if there is any asymmetry. the first downflooding point is marked on the large angle stability graph. Claughton. Also see: Select View from Analysis Data on page 159. will be ignored when computing the downflooding angle. deck edge and defined Key Points. ISBN 0-582-36857-X STABILITY INFORMATION BOOKLET available from the MCA. Emergence angles of the key points is also calculated – this is where they cross the waterline in an upward direction to become dry. Downflooding Angle After a Large Angle Stability analysis.
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. as opposed to the immersion angle which is when the cross the waterline in a downward direction. and an asterisk (*) is postfixed to the downflooding point‟s name in the Key Point Data table of the Results window.Chapter 3 Using Hydromax
Sailing Yacht Design: Practice. Adison Wesley Longman 1998. Wellicome and Shenoi. In addition.gov. These downflooding points will appear italicised. becoming wet.

Chapter 3 Using Hydromax

Equilibrium Analysis

Equilibrium analysis lets you determine the draft, heel and trim of the hull as a result of the loads applied in the table in the Loadcase window. The analysis can be carried out in flat water or in a waveform.
Choosing Equilibrium Analysis

The following environments can be applied to the Equilibrium analysis:
Fluid simulation of tank fluid centre of gravity Density Wave Form (if any) Damage (or Intact) from the Analysis toolbar Grounding (if any) Criteria

Height/freeboard above free surface The freeboard of each Key Point is also calculated. The freeboard is for the vessel condition currently displayed in the Design view and is recalculated after each Equilibrium and Specified Conditions analysis. The freeboard calculated is the vertical distance of the Key Point above the local free surface; hence the local free surface height if a waveform is selected will be taken into account.

Freeboard of key points.

Negative freeboards, i.e. where the Key Points are immersed are displayed in red. The longitudinal positions at which the minimum freeboard for the margin line and deck edge occurred are also specified. Stability Criteria Evaluation The criteria results are displayed in the Criteria tab in the results window.

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Chapter 3 Using Hydromax

Equilibrium Animation in Waves If performed in conjunction with analysis in waves, the Equilibrium analysis will automatically phase-step the waveform through a complete wavelength. This gives ten columns of results, one for each position of the wave crest. If necessary the results of this phase stepping can be animated giving a simple, quasi-static simulation of the hull motion in waves (Display | Animate). Note: This simulation only includes static behaviour at each wave phase, and does not cover dynamic or inertial forces. This can be done using Seakeeper.
Equilibrium Concept

The definition of equilibrium is “Position or state where object will remain if undisturbed”. You can distinguish equilibrium into two types:
Stable, when disturbed the object will return to its equilibrium position Unstable, when disturbed the object will not return to its equilibrium position

Stable equilibrium

Unstable equilibrium

With ships, an unstable equilibrium can exist when the KG > KM, i.e. the centre of gravity is above the metacentre (negative GMt). In real world a ship in unstable equilibrium will roll from the upright unstable equilibrium position to a position of stable equilibrium and assume an “angle of loll”. Since Hydromax starts the equilibrium analysis in upright position, it has no way of determining whether the equilibrium is stable or unstable. This means that unstable equilibrium may be found instead of the stable equilibrium. Therefore it is recommend to check the value of GMt yourself after doing an equilibrium analysis or perform a Large Angle Stability analysis and look at the slope of the GZ curve through the equilibrium heel angle.

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Chapter 3 Using Hydromax

Unstable equilibrium

Stable equilibrium ”Angle of loll”

The graph above shows the results of a Large Angle Stability analysis for a vessel with negative initial GMt. In practice this vessel would have a loll angle of approximately 25 degrees. If an equilibrium analysis is performed for this vessel with the transverse arm set to zero, Hydromax will find the unstable equilibrium position with zero degrees of heel. In practice, it is desirable to find the stable equilibrium position. To do this, first ensure that the tolerances (Edit | Preferences) are set as sensitive as possible. This will ensure that the smallest possible heeling moment is required to find stable equilibrium position. Then create a very small heeling moment by offsetting one of the weight items in the loadcase window TCG by just a fraction. The equilibrium analysis will now find the stable equilibrium position. Note: It is good practice to always perform a Large Angle Stability analysis as well as the equilibrium analysis to check if the vessel is in stable or unstable equilibrium. This is most likely to occur if the VCG is too high and the vessel has negative GM when upright. The problem can be overcome by offsetting the weight of the vessel transversely by a small amount.
Specified Conditions

Specified Condition analysis lets you determine the hydrostatic parameters of the vessel by specifying the heel, trim and immersion. Heel can be specified by either the angle of heel or the TCG and VCG. Trim can be specified by the actual trim measurement, or the LCG and VCG. Immersion can be specified by either the displacement or the draft.
Choosing Specified Conditions

Select Specified Conditions from the Analysis Type option in the Analysis menu or toolbar.

Three Sets of variables are provided, labelled Heel, Trim and Immersion. One choice must be made from each of these groups. Hydromax will then solve for the vessel hydrostatics at the conditions specified.

Values from the current loading condition can be inserted into the Centre of Gravity and Displacement fields by clicking on the Get Loadcase Values button. Also see: Setting the Frame of Reference on page 18 Specified Conditions on page 145 in the Analysis Settings section. Note: If the fluid simulation has been turned on in a previous analysis mode, then the VCG obtained from the loadcase will not include the free surface correction; the “Get Loadcase Values” button will return exactly the displacement and CG as displayed in the current loadcase window. The specified condition analysis itself ignores tank fillings and does no correction to VCG.
Specified Conditions Environment Options

The following environments can be applied to the Specified Condition analysis:
Density Wave Form (if any) Damage (or Intact) from the Analysis toolbar

Specified Conditions Results

The specified conditions results are the same as equilibrium analysis results except that criteria are not evaluated, i.e. hydrostatic data and key points freeboard are calculated.

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Chapter 3 Using Hydromax

KN Values Analysis

KN Values Analysis allows you to determine the hydrostatic properties of the hull at a range of heel angles and displacements to produce the cross curves of stability diagram.
Choosing KN Values Analysis

The analysis settings required for KN Values analysis are:
Heel from the Analysis menu, select range for analysis Trim (fixed or free) from the Analysis menu Displacement from the Analysis menu, select range for analysis and specify estimate of VCG if known

The heel angles used may differ from those used in the Large Angle Stability and Limiting KG analyses. To set the range of angles, select Heel from the Analysis menu. A range of displacements for KN calculations can be specified using the Displacement command from the Analysis menu. Initial and final displacements can be entered, together with the number of displacements required.

Displacement range dialog

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KN calculations are calculated assuming the VCG at the baseline (K). Traditionally. see: Trim on page 142 Also see KN Value Concepts on page 94
KN Values Analysis Environment Options
Density Wave Form (if any) Damage (or Intact) from the Analysis toolbar
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. the accuracy of the KN calculations (for VCGs in the vicinity of the estimated VCG) may be improved by calculating the GZ curve using the estimated VCG position – this will reduce the error in the trim balance due to the vertical separation of CG and CB because this vertical separation is specified more accurately than simply assuming the VCG at the baseline. If a VCG estimate is specified. However if the analysis is being calculated free-to-trim and an estimate of the VCG is known.Chapter 3 Using Hydromax
Trim dialog
The VCG can also be entered (specified from the vertical zero datum). the KN values are still presented in the normal manner with the KN values calculated as follows: KN(φ) = GZ(φ) + KG_estimated sin(φ) For information on Trim settings for KN Analysis.

select range for analysis Heel from the Analysis menu. select range for calculation of GZ curves Trim (fixed or free) from the Analysis menu
The range of displacements to be used is set in the same way as they are set in the KN analysis. The heel angles used may differ from those used in the Large Angle Stability and KN analyses. select Heel from the Analysis menu. notably angle of maximum GZ. To set the range of angles.Chapter 3 Using Hydromax
M
Z G
B’ B
N
K
Note: KN values can also be referred to as “Cross curves of stability”. see: Trim on page 142
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.
Choosing Limiting KG
Select Limiting KG from the Analysis Type option in the Analysis menu or toolbar. After each cycle. See Large Angle Stability on page 80 for further details. are extremely sensitive to the heel angle intervals that have been chosen. it is essential that the same heel angle intervals are used and that the free-totrim options and CG are the same. GZ curves are calculated for various KG values. For information on Trim settings for Limiting KG Analysis. the selected criteria are evaluated to determine whether the CG may be raised or must be lowered. Some criteria. When comparing the results of a limiting KG analysis to that of a Large Angle Stability analysis.
Limiting KG Settings
The initial conditions required for Limiting KG analysis are:
Displacement from the Analysis menu.
Limiting KG
Limiting KG analysis allows you to analyse the hull at a range of displacements to determine the highest value of KG that satisfies the selected stability criteria.

As well as the limiting KG. which is not necessarily the same as the zero point. it may be necessary to run the analysis heeling the vessel to both starboard and port (this can be done automatically in the Batch Analysis). trim and centre of gravity are given in the results table. you must still have at least one Large Angle Stability criterion selected.) Limiting KG calculations will be significantly faster if the trim is fixed.
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. for each displacement and the limiting criterion.
Limiting KG Environment Options
Density Wave Form (if any) Damage (or Intact) from the Analysis toolbar Criteria
Limiting KG Results
Limiting KG analysis results are
Limiting KG values. the minimum GM. you may wish to use a smaller number of heel angles than for the Large Angle Stability calculations. Criteria are only evaluated on the positive side of the GZ curve. However.Chapter 3 Using Hydromax
Note: Since Limiting KG can be quite a time consuming analysis. The Limiting KG analysis also checks that any selected equilibrium based criteria are passed at each VCG that it tries. (However this will cause some loss of accuracy. Limiting KG vs displacement graph
The Limiting KG value is measured from the baseline. draft amidships. so if there is any form of asymmetry.

Limiting KG Concepts
Hydromax will iterate to a KG value that just passes all criteria you have specified in the criteria dialog. problems can arise if the criterion is only available in its generic form – most commonly heeling arm criteria where the heeling arm is specified simply as a lever and not as a moment.Chapter 3 Using Hydromax
After a Limiting KG analysis has completed. rather than the heeling arm is constant). Where these values are explicit in the criterion‟s definition in Hydromax. Some criteria may depend on the vessel displacement and or vessel‟s VCG. 1 meter).1mm. If the criteria pass. since the heeling arm is not related to the vessel displacement in its definition within Hydromax. Hydromax will lower the KG and try again. Hydromax will raise the KG value and try to make the criteria fail. the results in the Criteria results table display “Not Analysed”. Important: For important information on varying displacement while evaluating criteria see Important note: heeling arm criteria dependent on displacement on page 240. In this case. If any of the criteria fail. If this tolerance is not achieved in a certain number of iterations. Also see: Convergence Error on page 146 in the Analysis Settings section. Hydromax will move on to the next displacement. Hydromax will start with a set start KG value (e. the correct values of displacement and VCG will be used in the evaluation of these criteria. However.
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.g. If you require the limiting KG for each criterion individually or wish to perform a Large Angle Stability and Equilibrium analysis at each of the displacements and the corresponding limiting KG. this can be done in the Batch Analysis. run a large angle stability analysis and check the selected criteria. the heeling arm will remain constant for all displacements (where it is perhaps desired that the heeling arm should vary with displacement. For example in the case where the heeling moment. this is because they do not necessarily refer to the final KG and would be misleading. Hydromax will continue doing this until the limiting KG value has been iterated to within 0.

The tanks would generally provide a transverse moment that must be balanced by the mass of the vessel. Hydromax assumes that raising the VCG will make criteria more likely to fail and that reducing the VCG will make the criteria more likely to pass. if only these types of criteria are selected.
Example calculations
It is probably simplest to explain this functionality by means of an example. However. 2. this should be zero). Note that we are only concerned about the tanks that will be damaged and that initially contain cargo or ballast. the intact vessel is upright (zero heel). Note that all results and input data will be assumed to be for the intact vessel. Current loadcase specifies initial loading of damaged tanks: This means that the currently selected Loadcase will be used to define the volume of cargo or ballast in tanks before damage is applied.e.Chapter 3 Using Hydromax
When performing a Limiting KG analysis. For Limiting KG calculations for a damaged vessel where some of the damaged tanks were initially non-empty. If this method is selected Hydromax will look at the mass and CG of cargo or ballast in tanks which will be damaged during the analysis. In this case. This is because under most circumstances. this is not seen as an additional mass because damage is computed by the lost buoyancy method. This is used to compute required TCG. Hydromax will evaluate any equilibriumbased criteria that are selected for testing and act accordingly. This is not necessarily the case for equilibrium-based criteria such as freeboard requirements or for GZ-based criteria such as Angle of maximum GZ. the mass and CG of the intact vessel after deducting the masses of cargo or ballast in any tanks that will be damaged. The second method was available in older versions of Hydromax and it is the first method that provides the additional functionality: 1. This is because to perform a sensible search. This functionality has been in Hydromax for many years. TCG and KG will also be for the intact vessel. which must therefore be offset. That is the specified displacement will be that of the intact vessel and that the resulting LCG. Hydromax must have at least one criterion that will improve by reducing the VCG. this can be specified below (if the vessel is symmetrical and initially upright. Hydromax assumes that damaged tanks lose all liquid cargo or ballast that they may have been carrying and their buoyancy is lost from the vessel – analysis is done by the lost buoyancy method rather than the added mass method.) Two methods of specifying the required TCG are possible. (Although seawater enters these damaged areas. If the vessel has an off-centre intact TCG. at least one GZbased criterion must also be selected. i. however the specified displacement and CG corresponds to that of the intact vessel with damaged tanks empty. Hydromax may have difficulty in finding a true limiting KG and specify convergence errors.
Limiting KG for damage conditions with initially loaded tanks
The set up of the Limiting KG analysis parameters has been modified to facilitate setting up the required TCG when calculating the Limiting KG for a damaged vessel where liquid cargo tanks initially carrying cargo or ballast water are damaged. it is often required to specify a required TCG. The second option is for the used to specify the required TCG directly.
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. this is because when they are damaged the ballast or cargo is assumed to be totally lost from the vessel.

the specified TCG is zero:
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. Importantly we shall also specify that the current loadcase should be used to determine the required TCG and because the vessel is symmetrical.25m by the stern. but with an initial vessel trim of 0. A vessel with a port-side tank that are initially full will have this tank damaged. We wish to find the maximum VCG that the intact vessel may have in order to pass the selected stability criteria.
Initial tank loadings
First we need to define how much cargo is in the tanks that will be damaged.
Use a loadcase to specify the initial quantities of fluids in tanks Setting the Displacements
Secondly we need to define the displacement range we wish to calculate the Limiting KG for. Here we have specified that the tank is 80% full before the damage is applied. This is done by defining a loadcase and switching to the intact mode to specify the tank filling levels. This is done in the Displacements dialog:
Displacement dialog Setting the Trim options
We now need to specify the trim options we wish to use. In this case we shall use free to trim.Chapter 3 Using Hydromax
The following sample calculations demonstrate how the new Limiting KG options may be used.

In this case the baseline (K) is at – 356.845mm
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. so the analysis should be done in this direction. these are filled significantly above the waterline so loss of ballast from these tanks will cause a list to Starboard. the stability criteria that need to be passed and a suitable range of heel angles to be computed to evaluate the criteria.Chapter 3 Using Hydromax
Trim and TCG specification Running the Analysis
We now need to select the damage case to be evaluated. We also need to determine which way we should heel the vessel and in doubt should try heeling the vessel in both directions to see which will give the worst result. In this case large port-side tanks are to be damaged. It must be remembered that these are KG results not VCG so when checking the VCG must be calculated.
Results from Limiting KG analysis
Limiting KG results Validation of results
The results can be validated by completing a Large Angle Stability analysis with the specified displacement and CG.

it can be seen that (as expected) the stability criterion is passed with a very small margin. Remember that these are the intact vessel displacement and CG:
Loadcase to check calculated Limiting KG
When the analysis is run.
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.Chapter 3 Using Hydromax
Model baseline
Computed VCG values
We can now set up a loadcase for one of the displacements.

Traditionally the criterion of margin line immersion is used to compute the Floodable Length curve.
Choosing Floodable Length 
Select Floodable Length from the Analysis Type option in the Analysis menu or toolbar. The range of displacements to be used is set in the same way as they are set in the KN and Limiting KG analyses. select range and specify VCG Permeability. The permeability dialog is used to specify the permeabilities to be used for the Floodable Length analysis. The results are presented as the maximum length of compartment plotted (or tabulated) against the longitudinal position of the compartment‟s centre. The analysis is always carried out free-to-trim. but the centre of gravity can either be specified directly in the Trim dialog or it is computed from the specified initial trim.
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.Chapter 3 Using Hydromax
Criterion is passed with a small margin
Floodable Length
The Floodable Length analysis allows you to calculate the longitudinal distribution of maximum length of compartments that can be flooded with the vessel still passing specified equilibrium criteria. For information on Trim settings for Floodable Length Analysis. The VCG must also be specified since the Floodable length analysis is very sensitive to accurate trim calculations. This means that the vertical separation of CG and CB is accounted for in the trim balance. The Floodable Length may be computed for a range of displacements and compartment permeabilities. see: Trim on page 142. select range Bulkhead location (if applicable)
1. the permeability is applied over the entire length of the vessel and is also applied to the free-surface when calculating the reduction of waterplane area and inertia. either initial trim or specified LCG) Displacement.
Floodable Length Analysis Settings
The initial conditions required for Floodable Length analysis are:
Trim (free-to-trim.

These are used to compute the Floodable Lengths. The Intact condition is automatically selected and the Damage toolbar is disabled Criteria from the Analysis menu. (The raw graph data can be accessed by double clicking the graph.) There are several graph plot options available in the Data | Data format dialog (when the floodable length graph is topmost). The vessel profile (centreline buttock) may also be displayed. All compartment standards up to the maximum specified will be plotted.Chapter 3 Using Hydromax
This permeability is unrelated to the permeability when defining compartments and is only used for floodable length calculations. The tabulated data is linearly interpolated from the graphical data. select which criteria should be evaluated
Criteria must be specified from the analysis menu.
Note that internally.
Floodable Length results
The results of the analysis are given in tabulated format at the stations defined in the Maxsurf Design Grid as well as graphical format.
Floodable Length Environment Options
Density Wave Form (if any) Damage: no damage case may be selected as this is automatically defined by the analysis. Hydromax will treat the vessel sinking or the trim exceeding +/-89º as a criterion failure.
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.

you can quickly adjust the bulkhead locations so that the vessel meets the required compartment standard. Plot the different compartment standards up to a specified maximum value.
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. the following dialog will be displayed. Vessel profile (shown in light grey) Floodable Length Bulkheads locations are specified in a table in the Input window. The compartment is then moved progressively forward along the vessel.
If the analysis is unable to find a condition where the vessel passes the selected criteria.
Floodable Length Concepts
The analysis is performed by defining a flooded compartment. with the centre of the compartment at a section under investigation.Chapter 3 Using Hydromax
Floodable lengths graph options:
Fix the y-axis so that it is the same scale as the x-axis. This process may be visualised by turning on the display of the Hydromax sections. The graph updates in real time as you adjust the bulkhead locations so once you have calculated the floodable lengths. The vessel sinking or the criteria failing in the intact condition could cause this. The length of this flooded compartment is increased section-by-section until one of the criteria is failed.

The speed of the analysis can be increased quite considerably by increasing the allowable tolerances in the Edit | Preferences dialog. it is recommended that a minimum of 100 sections be used for most situations.
Longitudinal Strength
Longitudinal Strength lets you determine the bending moments and shear forces created in the hull due to the loads applied in the Loadcase window. A trapezium shaped distributed load is derived from the centre and fore and aft extents of the load.
Choosing Longitudinal Strength
Select Longitudinal Strength from the Analysis Type option in the Analysis menu or toolbar. allowable shears and moments from Input window
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.
Longitudinal Strength Environment Options
Density Wave Form (if any) Damage (or Intact) from the Analysis toolbar Grounding (if any) Criteria.
Longitudinal Strength Settings
The initial conditions required for Longitudinal Strength analysis are:
Displacement and Centre of Gravity using the Loadcase window Distributed loads using the Loadcase window
When the Longitudinal Strength analysis mode is selected. two extra columns appear in the Loadcase window.Chapter 3 Using Hydromax
Note: Speed versus Accuracy The analysis will be both considerably more accurate and slower with a larger number of sections in the Hydromax model. See the Loadcase Longitudinally Distributed Loads section on page 45 for more details. The analysis can be carried out in flat water or in a specified waveform. These are used to specify the longitudinal extents of the load.

the net load. allowable shear forces and bending moments are overlayed on the graph. Upward acting forces such as buoyancy and grounding reactions are given negative values. such as normal masses in the loadcase or lost buoyancy due to damage.
Longitudinal Strength Results
The output from the longitudinal strength calculations is a graph of mass. buoyancy. From these. Downward acting masses. shear force and bending moment along the length of the hull are computed. For more information on how Hydromax can take fluids in tanks into account see Fluids Analysis Methods on page 148. are given positive values. Damaged tanks and compartments reduce the buoyancy. damage and non-buoyant volumes and grounding loads.
Name of Curve Mass Buoyancy
Grounding Damage/NBV Net Load Shear
Description Vessel mass / unit length Buoyancy distribution / unit length = immersed cross sectional area * density.Chapter 3 Using Hydromax
Note that Hydromax will always use the fluid simulation method when performing a longitudinal strength analysis. Grounding reaction Loas buoyancy due to damaged tanks and compartments and Non-Byoyant Volumes (NBV) Mass + Buoyancy + Grounding + Damage (and NBV)
x
Shear Force =
NetLoad ( x)dx
AftSt
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. If defined.

at a range of capacities. Tanks are taken into account as distributed loads as well based on their mass distribution that is calculated from the tank sections.
Choosing Tank Calibrations
Select Tank Calibrations from the Analysis Type option in the Analysis menu or toolbar. alternatively double-clicking in the graph will give you all the data as plotted.
Note: For the purposes of strength calculations. any point loads in the loadcase will be applied as a load evenly distributed 100mm either side of the position of the load. Also see:
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.Chapter 3 Using Hydromax
Moment Bending Moment = Allowable shear and moment
x
ShearForce( x)dx
AftSt
Allowable shear and bending moments as specified in the input Modulus table.
Tank Calibration Input
Tank definitions and boundaries Permeability Fluid type
The above data are specified in the Compartment and Sounding Pipes definition tables.
This data is also displayed in the “Long. Note Make sure you have defined sections in your model in Maxsurf. You can display this table by choosing Longitudinal Strength from the Results sub-menu under the Window menu. the longitudinal strength table will be empty. Strength” tab in the Results window. Without this.
Tank Calibrations
Tank Calibration allows you to determine the properties of the tanks you have defined in the Compartment window.

If Compartments or Non-buoyant volumes have also been calibrated. they are shown in grey. angle or trim measurement Heel angle range Which items to be calibrated: Analysis | Calibration options dialog
Analysis | Calibration options dialog: Compartments and Non-buoyant volumes may be calibrated if desired Tank Calibration Environment Options
Calibration intervals – see Sounding Pipes
Tank Calibration Results
If a range of heel (and / or trim) angles have been defined.Chapter 3 Using Hydromax
Relative Density of Tank Fluids on page 59
Tank Calibration Settings
Trim range. you may select which are displayed in the results table and graph using the Results toolbar.
You may chose which columns are displayed using the Data Format dialog:
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.

For more information see Chapter 5 Hydromax Reference.
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.Chapter 3 Using Hydromax
In the Window | Graphs menu each tank can be selected for display in the Graph window. These include the tank inertias about their centre of gravity.
Tank calibration calculations
A number of data are calculated for the tanks. the wetted surface area of the tank and the free-surface area.

where M and dm indicate an integration over the volume of fluid in the tank. near-full tank
Figure a shows a sounding pipe that extends the whole height of the tank. Figure b shows the vessel with (bow down) trim and a small amount of fluid in the tank. Here all tank filling levels will have a valid sounding. which is effectively what is happening in the figures below). Here there will be a range of tank filling levels which all show zero sounding. see below (increasing the trim. there are ranges of tank volumes that will show the same sounding/ullage.
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. Sounding pipes and tank calibration results
If the vessel is trimmed. will exacerbate this phenomenon):
Figure a Zero trim
Figure b Trim by bow. The following notation is used: x longitudinal-axis y transverse-axis z vertical axis
Calculation of tank inertias.Chapter 3 Using Hydromax
The wetted surface area of the tank includes only that part of the tank that is wet by the fluid in it at the corresponding sounding level. nearempty tank
Figure c Trim by bow. These points occur when the tank is near empty or near full. (The same effect can occur if the sounding pipe does not reach the lowest or highest point in the tank – remember that this can change as the vessel trims. The inertias are in fact “volume inertias” in that they are not multiplied by the density of the fluid in the tank. the top of the tank is only included when the tank is pressed-full. with the vessel at zero trim.

… . “Max” or a numerical value in the “Calibration Spacing” column of the Sounding Pipe definition table.9%.9%.1%. In the results out lined in red. 10%.
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. 98% and 100% full. 0. 90%.1%.
Sounding intervals
The sounding intervals for the calibration table may be:
Automatic. only – {100%}
In automatic mode the increments along the sounding pipe are chosen depending on the height of the tank to give approximately 20 soundings. 95%. see below. 85%. 98% and 100% full levels do not intersect the sounding pipe. The profile view of the tank in the trimmed vessel is shown on the right. 99. “F”. … . sounding pipe does not cover full range of tank capacities.0m but different capacities (the last but one calibration point is the fluid remaining in the tank when the sounding is 0. giving soundings of 0. 10%. 95%. 90%. this gives intervals of {0%.9%. there are four results which all have a sounding of 1.
In a similar way. the last two results are below the bottom of the sounding pipe. To specify the interval. the sounding pipe is in the middle of the tank and extends from the bottom to the top of the tank. 85%.9%. These effects will be noted in the tank calibration results if they are extreme enough since Hydromax always adds calibrations at 1%. 0. 5%. the sounding will be given as zero. Similarly if the 97. if the 1% level does not intersect the sounding pipe. Finally a “Fredyn” sounding list may be generated.Chapter 3 Using Hydromax
Figure c shows the vessel with the same trim. if the sounding pipe extends above or below the maximum and minimum fluid levels. you will get readings which have the same capacity but different soundings. but with the tank nearly full. 99. not the vertical step of the tank level). Here there will be a range of tank filling levels that all show maximum sounding.0m). the maximum sounding will be displayed.
Tank calibrations for severely trimmed vessels. type “A”. 97. 100%} of the full capacity of the tank. User defined Fredyn – {0%. In the blue results. Alternatively you may specify a precise sounding step (this is the step along the sounding pipe. 100%} Max. 5%.0m but different capacities – the fluid levels are all above the top of the sounding pipe.

0. Regulation 23: Accidental oil outflow performance Define the tanks in the Compartment definition window then choose the MARPOL analysis mode.117(52).0.
Fredyn sounding pipe
The tank calibration intervals required by Fredyn are (as a percentage of full capacity) {0. 95.0.
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. Seltect the Reolution and tanks to be included in the analysis in the MARPOL options (Analysis menu) dialog (see below).1. 90. If only the 100% full values are required “Max” may be specified for the calibratin spacing. 99. To use these intervals. all soundings for “Fredyn tanks” use this common sounding pipe. you must change the calibration intervals to Automatic or a positive value otherwise Hydromax will crash during the tank calibration analysis.
Fredyn calibration intervals
The tank calibrations normally follow regular length intervals along the sounding pipe.
MARPOL Oil Outflow
MARPOL probabilistic oil outflow calculation may be computed according to the following MARPOL regulations: Resolution MEPC. 5.Chapter 3 Using Hydromax
Note: Backward compatibility with earlier versions of Hydromax If the model is saved with Fredyn calibration intervals and is loaded into an earlier version of Hydromax. ….9}. 10.141(54). this sounding pipe starts at the vessel zero point and projects vertically upwards.0. A common sounding pipe is used for “Fredyn tanks”. Regulation 12A: Oil fuel tank protection Resolution MEPC. type “Fredyn” in the Calibration Spacing column of the Sounding Pipes Definition table:
Specification of Fredyn calibration intervals
Note that Compartments and non-buoyant volumes are always calibrated at the calibration intervals required by Fredyn.
MARPOL Options dialog (Analysis menu)
The MARPOL options dialog allows the user to select the tanks that should be included in the analysis for both MARPOL Regulations.

The table is in the MARPOL tab of the Results window:
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. the corresponding list of selected tanks will be displayed in the grid.Chapter 3 Using Hydromax
Tank selection for the MARPOL analysis
The list of selected tanks is different for both Regulations since Regulation 12A is for fuel tanks and Regulation 23 applies to cargo tanks. Further each tank has the option for being included in the computation for outflow due to side. Due to the nature of some of the measurements. it is not possible to guarantee that Hydromax will be 100% accurate in interpreting the measurements as defined in the MARPOL documents. When you select a Regulation with the radio buttons.and bottom-damage.
MARPOL Tank measurements
If the “Update all tank measurements” check-box is ticked. for this reason the user should carefully review the values generated by Hydromax. then Hydromax will attempt to measure the required tank parameters (over-writing any that have previously been manually edited). For this reason the data input and results are combined in one table.
MARPOL Results and additional Input
Because the calculations of the MARPOL analysis are very quick they are done in realtime as input data is edited by the user.

Main Hull Parameters
Different parameters are shown depending on the Regulation being used. Furthermore the inert gas overpressure may be specified for Regulation 23. If a parameter is modified. which affects bottomdamage outflow in Regulation 12A. Regulation 23 calculates the nominal oil density as the deadweight divided by the total tank capacity. the lightship draft is used to calculate the deadweight for Regulation 23 and the partial draft. the deadweight is computed as the difference in displacements between the deepest loadline draft and the lightship draft (or may be specified directly).Chapter 3 Using Hydromax
MARPOL calculations: Results Window
The table is split into three parts: main Hull parameters. The deepest loadline draft is taken as the DWL draft. oil outflow due to Side damage and finally oil outflow due to Bottom damage. please refer to the relevant IMO instruments. Parameters that can be edited are shown in black. For Regulation 12A. the nominal fuel oil density is specified by the user. those which cannot are shown in grey.
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. it is possible to revert back to the Hydromax calculated value or default by typing „H‟ or double clicking:
Reverting back to default/calculated parameter values
For full definitions of the parameters. the default being 1000kg/m3.

the MARPOL data may be saved.216(82) can be applied to both dry cargo and passenger ships whilst MSC. Note: Hydromax will overwrite user-edited tank parameters! Remember that any data that you change manually will be overwritten by Hydromax if the “Update all tank measurements” option is ticked in the MARPOL options dialog.19(58) . please refer to the relevant IMO instruments Saving
With the MARPOL sheet active. MSC. For tanks which are to be considered for both side. It is advisable to copy any manually edited data to a spreadsheet or text file if you only want to update the measurements of some tanks.19(58) is applicable to dry cargo vessels only.
For full definitions of the parameters.Chapter 3 Using Hydromax
Main hull parameters required for each Regulation Tank Parameters
Calculations are shown further down.damage.
Probabilistic Damage
IMO Probabilistic damage
Hydromax support for Probabilistic damage according to both IMO MSC.hmd file when the design is saved.
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. The user-editable tank parameters are the main dimensions which affect the probability of damage. listing first side-damage tanks. these values are linked so it is only necessary to edit them in one location. then bottomdamage tanks. it is also saved in the main .216(82) and IMO MSC.and bottom. These should be carefully checked since these can be difficult for Hydromax to automatically measure in some cases.

This is then compared with the required index. The log file parameters may be specified in the Edit | Preferences dialog:
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. It is useful to have this interaction because if the p Factor is too large for a particular zone. a p-factor can be calculated.
Maxsurf model is loaded as normal User defines (first selecting File | New to open the Probabilistic damage data table) other ship data required for the probabilistic damage analysis in the Damage window | Global table. the user may decide to refine the zone arrangement. The vessel‟s attained subdivision index is the sum of the products of the pfactors with their corresponding s-factors. User defines the damage zones they wish to consider in the Damage window | Zones table Once 2 and 3 have been completed.
During the analysis each GZ curve and details on the evaluation of the s-factor may be saved in a log file. The user can then perform the probabilistic damage analysis. User defines the bulkheads and deck values for single and groups of adjacent zones. The GZ curves are calculated for a large number of different damage conditions and several load cases. A first pass at this can be automatically generated using the Case | Extent of damage command. Hydromax runs a large angle stability analysis for each combination of loadcase and damage and collates the results to calculate the attained index. The same log file is used for each analysis so it is important to either change the name or copy the file at the end of the analysis if the results are to be kept. When the Zones have been defined the user can then define which tanks are damaged in each zone in the Damage window | Zone damage table.Chapter 3 Using Hydromax
Probabilistic damage – Principles
Essentially the probabilistic damage analysis performs a number of large angle stability analyses and uses the IMO criterion to determine an s-factor that depends on certain parameters of the GZ curve. The attained subdivision index can then be compared with a required subdivision index to see if the vessel achieves a sufficiently high degree of safety. For each condition. the p-factors Damage window | p Factors table are automatically calculated and displayed as the zone data is modified.
Flow through – Typical Use-case
The following section shows how the probabilistic damage analysis might typically be used.

these data would be lost. Chose the Probabilistic Damage analysis mode from the pull-down or Analysis menu:
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.hmd file.
Bring one of the probabilistic damage tables to the front to enable File menu items Probabilistic damage – Inputs
In this section we shall look at the input parameters required for the probabilistic damage analysis. most of the settings that are applicable to the Large Angle Stability analysis are also applicable to the Probabilistic Damage Analysis. To load or save the probabilistic damage data as a separate file. However this is new to version 14. For this reason it is also possible to save the probabilistic damage data as a separate file (in a similar way to the other Hydromax input data).Chapter 3 Using Hydromax
A Probabilistic Damage toolbar button is available in the Windows toolbar which will take the user back to the last used probabilistic damage input table:
Probabilistic damage – Saving input parameters
The probabilistic damage data is saved in the .
Settings for Probabilistic damage GZ curve calculation
Since the analysis essentially consists of a large number of GZ curve calculations. ensure that one of the probabilistic damage data sheets in the Damage window is on top.1 and if the file were read into an earlier version of Hydromax and saved.

Chapter 3 Using Hydromax

Selecting Probabilistic Damage anlysis mode

Once you have selected the probabilistic damage analysis mode, you can define the heel angle range and trim settings to be used as well as any environmental parameters such as waveform (as well as the fluid analysis method to be used). During probabilistic damage analysis, it is possible to check the vessel heeling to both port and starboard. This is useful if the tanks contain ballast or cargo and it is uncertain in which direction the vessel will list when damaged (or indeed the vessel may list to different directions depending on the loadcase and damage). Hydromax will calculate the GZ curve in both directions and, if the criteria can be evaluated in both directions, the lowest s-factor will be taken. If the criteria can only be evaluated in one direction, then this value for the s-factor will be taken. It is recommended to evaluate at least one negative heel angle and the direction of heel should correspond to the side of the vessel that is being damaged (see below):

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Chapter 3 Using Hydromax

Heel angle specification (as per Large Angle Stability)

Use either fixed trim or free to trim to loadcase. s-factor calculation

The s-factors are calculated by stability criteria. The Probailistic damage analysis has its own set of criteria (though the same parent criteria are also available in the large angle stability analysis criteria). When the analysis mode has been set to Proababilistic Damage, you will see the criteria that are used for this analysis. The number of parent criteria is reduced to only those which can calculate the s-factor. Also some “Default” criteria are supplied, you can add or modify these should you so desire. When running the analysis, Hydromax will look at the probabilistic criteria that have been selected and warn you if there are any problems.

The following rules should be observed when defining the probabilistic damage criteria:
As with the normal criteria manager, changes made to the parent (bold) criteria are not saved. If you need to modify any of the criteria you should make your own copies of the parent criteria A set of Default criteria are provided – these can be modified and changes will be saved. Only one criterion should be selected and it should correspond to the IMO Resolution being used. (Strictly, you may have up to one of each MSC.216(82) or MSC.19(58) criteria selected and Hydromax will automatically use the appropriate one – according to the selected Resolution in the Global sheet – but for clarity, it is probably best practive to just have a single criterion selected.) The criteria should always be selected for Damage analysis. Hydromax will automatically update some of the criteria parameters according to corresponding parameters in the probabilistic damage setup. However it is still good practice to review criteria parameters before starting the analysis. This is particularly true for the MSC.216(82) Resolution where the vessel type and heeling moments must be defined correctly. The criteria window can be closed with either of the close buttons.

For further information on how the s-factors are calculated and the different parameters, please refer to the Criteria Help section for the appropriate criteria (and heeling arms).
Main parameters and calculation of required subdivision index

The other parameters required for the probabilistic damage analysis are defined in the last four tables in the Damage window:

Depending on the selected IMO Resolution, different rows and columns will be displayed in the tables; both MSC.216(82) and MSC.19(58) are provided, A.265 VIII is not included. Tool tips have been added to provide a more detailed explanation of the input parameters and also the options available.

Tool tips for Global data sheet Global table

This table is used to define the main parameters for the probabilistic damage anlysis as well as provide some intermediate calculations. Input data are shown in black whilst results are shown in grey. Depending on the Resolution and vessel type, some rows may be hidden.

Name of loadcase that defines the vessel at the deepest subdivision draft. Name of loadcase that defines the vessel at the partial subdivision draft. Name of loadcase that defines the vessel at the light subdivision draft. not required for MSC.19(58). Vessle type. not required for MSC.19(58). Number of persons for whom lifeboats are provided. required for MSC.216(82), pax. Vessel only. Number of persons inclusing officers and crew that the vessel is permitted to carry in excess of N_1. required for MSC.216(82), pax. Vessel only. Parameter not currently used.

Specifies the upper limit of the number of adjacent zones that should be damaged. If you wish to limit the analysis by p-factor only, then specify the number of zones here (see min p-factor below). Specifies the minimum p-factor for which an analysis should be performed. The maximum a condition can contribute to the

Chapter 3 Using Hydromax
max. then the s-factor will be taken as zero (irrespective of the GZ curve). Fore and aft extents of the zone boundaries are input by the user and the length and centre of the zone is automatically calculated. the boundaries of adjacent zones are automatically updated if required. This will ensure that conditions with zero p-factor will still be evaluated. If desired the vertical extent of damage (when automatically generating the zone damage) can be limited. If you wish the analysis to be purely limited by the number of adjacent zones (see above) then specify a small negative value. If the vessel trim exceeds this value. with a number of complete rows selected) to add or delete zones. as are the zone names. but the option to start from the bow is also allowed in Hydromax
The next table (Zones) allows for the definition of the longitudinal damage zones. It is normal to begin the Zone numbering at the stern. The heel direction in the Heel setup should correspond to the side of the vessel being damaged. vertical extent of damage Damaged side -Starboard or Port
Zone 1 located at bow or stern?
Longitudinal Zone definition
attained index is the p-factor. this can speed up the analysis. As for other similar tables. If the the p-factor is very small the contribution to the attained index will be negligible and there is little point in carrying out the analysis. trim angle to consider Limit vertical extent of damage? max. The subdivision length is taken as the limits of the length defined by the zones. If desired the vertical extent of damage (when automatically generating the zone damage) can be limited. This can speed up the analysis. The extent of damage is assumed to go all the way to the centreline but you may specify which side of the vessel is damaged. use Edit | Add or Delete (or Ctrl+A or Del key.
Damage zones defined by fwd and aft boundaries
Zones may be shown in the drawing views (this display option is only available in Probabilistic Damage analysis mode):
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. Specifies which side of the vessel will be damaged (when automatically generating the zone damage). Conditions whose pfactor is below this minimum will not be evaluated.

the probability of damaging a longitudinal zone or group of adjacent zones is calculated as well as the cumulative probability. A subtotal for the pfactor for a given number of adjacent zones is given as well as a cumulative to total for all the p-factors. This will help the user to determine the maximum number of adjacent zones that should be analysed. The last column shows whether a particular condition will be tested (if the p-factor is sufficiently large and the maximum number of adjacent zones is not exceeded).216(82) or MSC. P-Factors
From the damage zone calculations.19(58) made in the Global table.
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. The columns displayed depends on the choice of Resolution: MSC. it probably makes more sense to limit the analysis by specifying a desired minimum p-factor rather than a number of adjacent zones.Chapter 3 Using Hydromax
Probabilistic damage zones (stbd. All combinations of adjacent zones are calculated at this point. This can easily be done by specifying the maximum number of adjacent zones as the number of zones defined. side damage) shown in pink. In practice.

there is a special way of calculating the b-value and this needs to be done for each set of adjacent zones. measured from the side-shell. it is also possible to define sub-zones due to longitudinal bulkheads (transverse subdivision) and decks (vertical subdivision). A column is provided for the user to specify the side-shell offset (from the centerline) and this is used only to draw the transverse extents of the damage zone. Note that there is one extra r-factor than the number of bulkheads – this represents the probability of damaging to the centerline. but also for groups of adjacent zones. the zone will be damaged up to (but not across) the centreline.
Transverse sub-zone definition and R-Factors
Transverse sub-zone definition allows the user to limit the damage penetration to a certain distance into the vessel towards the centerline. This is because where the side-shell or bulkhead is not parallel to the centerline.Chapter 3 Using Hydromax
p-factor calculations for individual and groups of zones Sub zones due to transverse and vertical subdivision
As well as the main longitudinal subdivision. The r-factors are then calculated for each of the b-values that have been defined. the inner limit being at a distance side-shell offset minus b from the centreline.
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. The sum of all r-factors should be unity (a check is provided). The b-values are defined not only for each individual zone. The side-shell offset value defaults to the maximum halfbeam of the vessel. If no b-values are specified. I have followed IMO notation by specifying the penetration depth from the side-shell (rather than specifying the offset from the centerline).

Chapter 3 Using Hydromax
Visualisation of zones and sub-zones: sub-zones shown dashed. This can also be seen in rendered view to quite effectively visualize the damage. selected zone shown in bold.
The currently selected zone or sub-zone is shown in bold as well as any damage for that zone.
Clicking in a zone or sub-zone in the table highlights the zone graphically
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.

The loadcase for v-factor calculations is selected by clicking on the desired loadcase in the Global table. the v-factors will be automatically recalculated for the loadcase under consideration.
Loadcase for v-factor calculations is selected by clicking on the desired loadcase in the Global table.
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. Thus we introduce the concept of the currently selected Loadcase for the displayed vfactors. Note that during the full probabilistic damage analysis.Chapter 3 Using Hydromax
Vertical sub-zone definition and V-Factors
Similarly decks may be defined to create vertical subdivision of the zones. but these also depend on the draft of the vessel. The corresponding v-factors are calculated.

The “Zone damage” tab of the Damage window must be on top to enable this command. From this Hydromax can work out what should be damaged for any combination of adjacent damaged zones. this can be modified by the user should this prove to be necessary (or it can be defined from scratch by the user). if the pfactor exceeds the minimum values specified (again in the Global tab).
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. Damage cases will be added up to the maximum number of adjacent zones specified in the Global tab. The Damage window must be on top for this command to work.
Automatic definition of damage for each zone
Additionally the user may automatically generate damage cases for the Zone damage that has been defined damage configurations within the maximum number of adjacent zones range and above the minimum p-factor will be added.
Definition of whats damaged in each zone
Once the zones are defined the user can select the Case | Extent of damage command and this will automatically generate the zone damage according to which tanks lie within the zone boundaries. but has been added for convenience should the user wish to manually run large angle stability analyses for the same damage cases. Once the automatic damage is defined.Chapter 3 Using Hydromax
Zone damage
The zone damage sheet specifies which tanks are damaged for a given zone. This stage is not required for the probabilistic analysis.

The zone is selected by clicking in the corresponding column of the Zone Damage table.Chapter 3 Using Hydromax
Automatic creation of damage cases using the damage defined for each zone Visualization of zone damage
When in Probabilistic damage analysis mode the damaged tanks and compartments displayed are not those of the current damage case. but those of the currently selected zone.
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.

2
Thess values are defined in the Permeabilities table in the Probabilistic Damage window. but they are not updated if they are then changed in the Compartment definition window.
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. When you generate new probabilistic damage data. the permeabilities are the same as the damage permeabilities given in the Compartment Definition table.Chapter 3 Using Hydromax
Zone damage visualisation Probabilistic damage permeabilities
It is possible to define different permeabilities to be used for tanks and compartments for the different load conditions – as required for “cargo compartments” in MSC. but these can be overridden (for the probabilistic damage analysis only) for each draft if desired. the permeability values are copied from the Compartment definition. By default.216(82) Regulation 7-3.216(82) Regulation 7-3.2:
MSC.

Hydromax will make several checks to see if the analysis parameters have been correctly set up.Chapter 3 Using Hydromax
In the log file. These are not exhaustive tests but should pick up critical errors. the permeability used for any damaged tanks is shown:
Probabilistic damage – Analysis
Once the analysis parameter data has been defined. it is worth checking that the heel direction (Analysis | Heel) is correct and also check that the s-factor calculation parameters are corerect (Analysis | Criteria)
Pre-run checks
When trying to run the probabilistic damage analysis. The following checks are made:
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.

Should the vessel sink.Chapter 3 Using Hydromax
That loadcases that have been specified exist That the vessel type is correct in the criteria (if MSC.216(82) is being used) That the correct s-factor criterion has been selected. Note that only one criterion may be selected. this is reported and the s-factor given as zero. excessive trim occur or the large angle stability analysis fail to converge. The required index is also shown as well as pass/fail status.
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. Basic data pertinent to calculation of the s-factor is also presented as well as a total Attained subdivision index at the bottom of the table. If Hydromax finds no criteria selected but a suitable one is available (but unselected) then it will prompt the user to use this one:
Analysis
Large angle stability analyses are computed for each combination of loadcase and zone damage up to either the specified maximum number of adjacent zones or the minimum specified p-factor.

If you have stopped the analysis. If you are not interested in seeing the progress of the analysis. including all the GZ results and criteria evaluation for each loadcase / damage case combination are logged during the analysis.Chapter 3 Using Hydromax
Probabilistic analysis results Probabilistic damage – Future developments
The probabilistic damage analysis is still under development and new features will be added in subsequent versions of Hydromax. There may be a slight time delay on all of these operations while the current cycle is finished. Hydromax will flash and beep to indicate that the analysis has been completed. You can also switch application by clicking in the window of any background program. Hydromax will continue to calculate in the background although its speed will be reduced. Hydromax will redraw the contents of the windows to display the current hull position for each iteration. you can resume calculation by selecting Resume Analysis from the Analysis Menu or toolbar. floating the hull to equilibrium conditions where required. Should the analysis take longer than about 45 seconds. choose Start Analysis from the Analysis menu or toolbar. The logfile location is specified in the Preferences dialog:
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. Hydromax will step through the parameter ranges specified. pause and resume functions are also available in the Analysis toolbar:
Probabilistic damage Log file
All the intermediate results.
Starting and Stopping Analyses
To start the analysis. The start. Calculations may be interrupted at any time by selecting Stop Analysis from the Analysis menu or toolbar. switch to a table window and maximise it to speed up the analysis. The drawing of the vessel at each step of the analysis can be quite time consuming.

For the Limiting KG analysis you may also check the Limiting KG for each criterion individually.Chapter 3 Using Hydromax
Probabilistic Damage analysis logging
Batch Analysis
Batch Analysis Concepts
Hydromax has basic batch processing capability. Further. The aim of the batch processing function is to:
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. With a single command. Limiting KG and KN calculations can be made for each damage condition. Hydromax will run Large Angle Stability and Equilibrium analyses for all combinations of load and damage cases. You may also choose to perform a Large Angle Stability and Equilibrium analysis at the final VCG. There are other options which allow the analysis to be performed heeling to both port and starboard.

key points. i. criteria and analysis parameters for the required analyses have been set up. the Batch Analysis is started
Analysis | Start Batch Analysis
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. Provide all relevant results and the data required to be able to reproduce the runs.: analysis parameters.
Before you can perform a Batch Analysis it is recommended that you run a number of Analyses manually to check whether the Model has been defined correctly and all Analysis Settings and Environment conditions have been set correctly. Facilitate time consuming Limiting KG analyses. file name etc. Facilitate testing with heel to port and starboard for vessels with asymmetric loading and/or damage conditions (or hulls). damage cases. especially where results for all individual criteria are required. Enable Limiting KG and KN analyses to be performed automatically for all damage cases. Facilitate export of the data from Hydromax and import into MS Excel for post processing and report generation.Chapter 3 Using Hydromax
Provide the user with a simple and consistent way of carrying out Large Angle Stability and Equilibrium analyses on a large number of load and damage cases.
Batch Analysis – Procedures
Once the loadcases.e.

At the bottom of the dialog is a check box which allows users to select whether the results of a batch analysis should go to the Report window in Hydromax as well as the batch analysis text file. only the results of the final analysis will be stored in Hydromax. this tab delimited text file may be imported directly into MS Excel for further processing. it is advisable not to include the results in the report. you will be prompted to enter the name and location of the file where Hydromax will write the results of the batch analysis. if you want the Large Angle Stability to use a fixed trim of 0.Chapter 3 Using Hydromax
Batch analysis runs all combination of loadcases and damage cases. Warning: Sending the results to the Report can slow down analysis considerably and also consume considerable system resources. minimising Hydromax can reduce the time required to perform the calculations.
Batch Analysis Results
Before analysis starts. Any criteria that have been set are evaluated at the end of each analysis and the results of these are also output to the text file. heel angles etc. the batch analysis will automatically create a Word document. For large batch analysis. Important: For important information on varying displacement while evaluating criteria. Also see: Reporting on page 155.
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. see Important note: heeling arm criteria dependent on displacement on page 240. it is not possible to go back to the results for a specific analysis from within Hydromax. This is because time consuming redrawing of the design windows. The report is stored in memory and if you have insufficient memory.
Batch Analysis Settings
Analysis parameters such as trim. When the option for Sending the results to Word is selected in the Edit | Preferences dialog. Because the analyses are simply carried out one after the other. are set in the normal way for each analysis type included in the Batch analysis.5 m:
first select the Large Angle Stability analysis type from the analysis menu set the trim to Fixed trim and 0. For example. Once the analysis is complete. it is possible that your computer will become very slow to respond and under some circumstances with certain operating systems even cause Hydromax to crash.
Tip: Under most operating systems. graphs and tables is avoided.5 m then select Analysis | Batch Analysis
Batch Analysis Environment Options (Criteria)
Any Analysis Environment Options specified prior to a Batch Analysis will be used during the Batch Analysis.

For an equilibrium analysis all degrees of freedom are derived from the centre of gravity and Displacement. KN and Limiting KG analyses.
Heel
The Heel dialog from the analysis menu is used to specify the range of heel angles to be used for Large Angle Stability. For example: it can match a specified heel. In hydrostatic analysis. simply put 0 in the other steps. Hydromax matches the trim. Combinations of both are also possible. trim and draft.Chapter 3 Using Hydromax
Analysis Settings
In the previous sections opening and preparing a model in Hydromax was discussed together with descriptions of the different Analysis types. If only one set of steps is required. In this case the LCB and TCB (and therefore the required LCG and TCG) are calculated from the underwater hullshape at each draft.
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. Heel angles between 180 and +180 may be specified. This section will describe the following analysis settings:
Heel Trim Draft Displacement Specified Conditions Permeability
Hydromax will allow specification of only those analysis settings that apply to the currently selected analysis type. because vertical centre of gravity is also important and also because most of the variables are coupled. or it can match a specified displacement and centre of gravity by varying the heel. trim and draft by varying the displacement and centre of gravity. The various analysis types and settings can be thought of as setting one variable in each pair to a fixed value and deriving the others from the analysis. Heel and Draft. For example: the Upright Hydrostatics analysis consists of fixing heel and trim and stepping through a series of fixed drafts. heel and draft with the vessel‟s mass and centre of gravity or visa versa. This way the volume of the displaced hull matches the required mass and the centres of gravity and buoyancy lie one above the other in a vertical line. The heel steps must be positive. The following table is a very simplified representation of the degrees of freedom and their weight counterpart: Degree of Freedom Draft Trim Heel Weight Displacement Longitudinal Centre of Gravity (LCG) Transverse Centre of Gravity (TCG)
1 2 3
In fact it is a rather more complicated situation than that suggested by the table above. In the Specified Condition Analysis any combination of the variable pairs may be specified. there are three degrees of freedom: Trim.

It is possible that the GZ at zero heel may be very slightly positive (due to asymmetry or rounding error) for this reason.Chapter 3 Using Hydromax
If there is any asymmetry in the vessel due to either: hull shape.) Equilibrium and Longitudinal Strength analyses always use a free trimming (and free heeling) analysis so that there is no trimming (or heeling) moment applied to the vessel at the final equilibrium. Hydromax will fit a cubic spline to the GZ curve and use this to interpolate for values between the tested heel angles. etc. it is advisable to test at least one negative heel angle. then the analysis should be carried out for both heel to starboard and heel to port to find the most pessimistic condition. (For the Specified Condition analysis. it is essential that the GZ curve crosses the GZ=0 axis with positive slope. Hydromax will not do any curve fitting and linear interpolation will be used. to ensure that the equilibrium angle is identified. Note: For the angle of equilibrium to be found (when analysing criteria). at say -5 degrees. It is good practise to start the heel range at an angle of approximately -30°. the trim may be specified in the Specified Conditions dialog.
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. and there is any doubt as to which will be the worst heel direction.. If all the heel angle intervals are 10 deg or less. Select Trim in the Analysis menu to bring up the Trim dialog. loading. Trim may be specified for Upright Hydrostatics. damage. Large Angle Stability. This is to allow roll back angle criteria to be evaluated correctly. This can be a source of apparent differences in the results from the different analyses.
Note: The heel angles to be used are specified independently for each analysis mode. Floodable Length and Tank Calibrations.
Trim
For most analyses you may specify whether the vessel is free-to-trim or has fixed trim. key points. KN Analysis Limiting KG. If any step is greater than 10 deg.

In the case of the Limiting KG analysis. Thus. The TCG and VCG are specified directly. This is for when a range of displacements is used for the analysis: Limiting KG.
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.
Fixed trim (KN and Limiting KG analyses only). Floodable Length. In this case. so cannot be specified. Although considerably faster. Equilibrium. intact vessel floats at a specified trim. this analysis will tend to overestimate ship stability properties such as GZ. Free to trim to loadcase – the analysis trims the vessel to the CG specified in the loadcase. Probabilistic Damage. The analysis is carried out with the specified fixed trim. Free to trim to specified CG – this is again free-to-trim but the CG is specified in the dialog. Calculations at each heel angle of the large angle stability analysis are then done free-to-trim using the derived LCG and VCG. Free-to-trim using a specified initial trim value Using this method. 3. the VCG is being found by the analysis. Probabilistic Damage) as well as Upright Hydrostatics and Tank Calibrations 2. KN. for each displacement. KN. Fixed trim – the analysis is carried out at a fixed. intact vessel trim will be the same. Longitudinal Strength. Limiting KG. specified initial trim. heel is not considered thus TCG cannot be specified. the vessel is not free-totrim as it heels. the upright. The LCG is calculated using this value and the VCG. This applies to all analyses that carry out a large angle stability-type analysis (Large Angle Stability. all three components of the CG need to be know. for each displacement. This it is possible to specify the LCG either directly or so that the upright.
Specification of different trim options is dependent on the type of analysis currently selected.Chapter 3 Using Hydromax
Essentially there are three options for trim: 1. the LCB of the intact vessel at the specified trim and zero heel is computed. This option is available for all analyses that have a loadcase: Large Angle Stability. For the Floodable Length analysis. but the LCG will be different.

any liquid cargo should also be removed from the model. (As the trim angle increases the longitudinal movement of the centre of gravity due to its vertical position becomes more important. For Floodable Length calculations. the VCG is needed to provide an accurate balance of the trimming moment. but the upright vessel trim will be different. Thus. the VCG will only have an effect if the analysis is free-to-trim. may be specified. This LCG is then used to compute the free-to-trim vessel orientation at each heel angle as the large angle stability analysis is performed. The TCG can be either specified directly or calculated from the tank loadings defined in the current loadcase. a specified constant LCG is maintained for each displacement. there is an option to automatically adjust the displacement and LCG of the vessel so that liquid cargo of damaged tanks is removed from the model. For KN analysis.Chapter 3 Using Hydromax
Free-to-trim to a specified LCG value With this method. so to be consistent. the LCG will be the same. measured from the vertical zero datum (not necessarily KG). It will also be used to improve the accuracy of the KN results. This is especially useful when evaluating the Limiting KG of a damaged vessel that had cargo or ballast in tanks which are subsequently damaged. the actual VCG is used and the VCG input field will state “not applicable”. the VCG will be used to calculate the LCG if an initial trim value is specified.
Current Loadcase specifies initial loading of damaged tanks (los mass during analysis)
Finally. for each displacement.) In the case of the Limiting KG analysis.
Draft
The draft dialog is used to specify the range of drafts to be used for the Upright hydrostatics analysis. which are always calculated free-to-trim. for the Limiting KG analysis. VCG for trim balance The VCG. Also. because the analysis is very sensitive to trim.
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. This is for consistency with the lost buoyancy analysis method: the buoyancy contribution of damaged tanks is removed from the model. It will be used to determine the LCG if an initial trim value is specified. TCG value The TCG option allows you to specify an off-centreline centre of gravity for Limiting KG and KN calculations.

Individual Permeability of Tanks and Compartments
The individual permeability of each compartment (or tank) is specified in the Compartment definition table. and is specified in terms of KG – i. Use the Add and Delete buttons to add or delete rows from the table.
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. The compartment.e.
Displacement
The displacement dialog is used to specify the range of displacements to be used for the KN. the permeability is applied over the entire length of the vessel. Limiting KG and Floodable Length calculations.
The Permeability dialog is used to specify the permeabilities to be used for the Floodable Length analysis. from the baseline. The permeabilities may be sorted by double clicking on the permeability column heading. tank or non-buoyant volume permeability and is only used for floodable length calculations.
Permeability
The Permeabilities are set in a table in the Permeability dialog. This permeability is unrelated to compartment. tank and non-buoyant volume permeabilities are used when calculating the effects of damage. The last set of permeabilities used will be recalled from the registry when Hydromax is started.
Specified Conditions
The specified conditions analysis setting is only available for the specified condition analysis. See Specified Conditions on page 90. and/or calculating the weights of fluids in tanks in the loadcase. which is not necessarily the vertical zero datum.Chapter 3 Using Hydromax
The VCG specified in the draft dialog is used for the calculation of upright stability characteristics such as GMt only.

001% to 1. calculation tolerances can be set.
One of the most common causes of non-convergence is if the specified displacement exceeds the volume of the completely submerged vessel and it sinks. Also convergence may be poor if the trim angle approaches 90 . If convergence to within the acceptable error has not been achieved. If this is not achieved within a certain number of iterations. Acceptable tolerances should always be greater than Ideal tolerances. Hydromax will display a warning. The warning is also not shown when accessing Hydromax from a VBA macro using the Automation interface
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.
Convergence Error
Hydromax will attempt to solve most analysis to within the ideal tolerance. Note This warning is not displayed during batch analysis. Hydromax will continue.00001% and 0.0%. but the acceptable error has been achieved. The specified displacement and the actual displacement at the current iteration are provided for information.1% (1 gram in 10 tonnes of displacement).Chapter 3 Using Hydromax
Also see: Modelling Compartments on page 51
Tolerances
In the Edit | Preferences dialog. This defines the tolerances that Hydromax uses to determine when to finish iteration during
Large Angle Stability Equilibrium analysis Specified conditions KN calculations Floodable Length Longitudinal Strength
Ideal tolerances can range between 0. If Hydromax thinks that it is likely that the model has sunk (waterplane area is zero at the current condition) the following dialog will be displayed. Acceptable tolerances can range from 0. instead the warning is written in the batch file.

producing a highly non-linear waterplane area vs. If the search is unsuccessful after a reasonable period of time. you can interrupt Hydromax by pausing the analysis. in the case of the Floodable Length analysis. but will allow you the option of continuing the search. which appears not to be due to sinking.
Analysis Environment Options
The analysis can be performed in different environments. draft plot. trim angle curve or moment to heel vs. this limit is increased to +/-89º. Other causes of non-convergence can be non-linear moment to trim vs.Chapter 3 Using Hydromax
If there is a convergence problem. Note: There are occasions when convergence will not necessarily occur within the maximum allowable number of iterations. If Hydromax fails to converge it will give you a warning. If you choose to continue. heel angle curve.
This problem can sometimes occur if the specified displacement is extremely small and the vessel has a large flat bottom. The analysis will also fail to converge if the trim becomes excessive. All analyses other than Floodable Length will fail if the trim exceeds +/-45º. this section describes the analysis environment options available in Hydromax in more detail:
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. then the following dialog will be displayed. Hydromax will search for the equilibrium position indefinitely.

e. if the filling level is less than or equal to the lower limit or the filling level is greater than or equal to the upper limit. This is applicable to the “IMO” free surface moment type only. but the code provides some flexibility in interpretation for the lower limit. (see IMO IS Code)
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. This requires that a nominal minimum displacement be specified.e. This functionality is accessed through the Analysis | Fluids dialog:
Fluid Analysis dialog
If the corrected the VCG method is used. the FSM is applied if the filling level is within the exclusive range specified.2 Free surface effects should be considered whenever the filling level in a tank is less than 98% of full condition.10 The usual remainder of liquids in empty tanks need not be taken into account in calculating the corrections.3.
3. It is possible to specify the range of filling levels for which free surface moments should be applied in the loadcase. provided that the total of such residual liquids does not constitute a significant free surface effect. You may set different limits for each of the different free surface moment types other than “User Specified”.
In addition it is possible to ignore the free surface moment if the VCG correction for a single tank. the free surface moment will be zero. The upper limit is clearly stated by IMO as 98%. Selecting Fluids in the Analysis menu opens the Fluids Analysis dialog. Free surface effects need not be considered where a tank is nominally full . filling level is 98% or above.i. due to the free surface moment is less than a specified amount.Chapter 3 Using Hydromax
Fluids Analysis Methods Density Waveform Grounding Stability Criteria Damage
Fluids Analysis Methods
Hydromax allows you to specify two different ways of simulating any fluids contained in tanks or compartments. i. (see IMO IS Code) 3.3.

9 Small tanks which satisfy the following condition using the values of "k" corresponding to an angle of inclination of 30°.Chapter 3 Using Hydromax
3. It is reasonably accurate at low angles of heel and trim.
Fluid analysis method: Use corrected VCG
Tank capacities and free surface moments are calculated for the upright hull (zero trim and zero heel).01m
min
where M fs is the free surface moment of the tank in question and
is
the ship displacement at the minimum mean service draft of the ship without cargo. calculated in the upright condition. need not be included in the correction:
M fs /
min
0.3.
Note: Calculation of GM GM values always use the centre of gravity corrected for free surface moments even if the “simulate fluid” option has been chosen. Although the computational potential is available. This method should be used when compiling a stability booklet for a design. authorities have not adopted this more accurate calculation of the shift in centre of gravity due to fluid movement. Note that the upright free surface moments as shown in the loadcase are used. There are several FSM types available. This is because the actual free surface moment to be used to determine the VCG in a loadcase depends on the method being used and also the heel angle in question (in the case of the IMO correction). For more information. These values are automatically calculated from the maximum free surface moments of the tanks. with 10% stores and minimum water ballast. The effective rise in VCG due to the tanks' free surface is calculated by summing the free surface moment of all the tanks and dividing by the total vessel displacement (the free surface moment to be applied is specified in the loadcase). see Working with Loadcases on page 38. if required. not those from the actual second moment of area of the inclined tank waterplane. the loading window will include a column for free surface moment and cells for corrected fluid VCG.
Note Most documented stability criteria assume that the corrected VCG method has been used. Note: Tank Calibration results In the tank calibration results the free-surface moment based on the transverse second moment of area of the tank waterplane is given for all filling levels.
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. In this case. as it corresponds with the traditional approach used by naval architects and classification societies worldwide.

The new centre of gravity is calculated for each tank and used in the analysis. the density of sea water (the fluid in which the vessel is floating) and fluids commonly carried on board can be adjusted using the Density dialog. Large Angle Stability.e. tall narrow tanks.
Density of Fluids
Where necessary. will be displayed in the View window. This approach is used when the stability of a vessel is being investigated and the closest possible simulation of the hull's behaviour is required. When fluid simulation is used in one of these analyses. however the results are significantly more accurate. Alternatively. density may be specified using Barrels as the unit of volume. or non-dimensional relative density (specific gravity). Density using the current units.
When selected. and GM. Equilibrium Condition and Longitudinal Strength (the Longitudinal Strength analysis always uses fluid simulation). KG. may be specified.
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. The penalty of using this approach is that the calculation time is longer.
When fluid simulation method is selected.0 kg/m3. free surface moments and corrected fluid VCG are normally not displayed in the loadcase. It is particularly useful at high angles of heel or trim. or with tanks whose heeled water plane area may be significantly different from the upright case (i. Hydromax iterates to find the fluid level for the rotated tank at the specified capacity.e. or wide shallow tanks). i. filled to the volume specified in the loadcase. Otherwise the complete tank will be shown. VCG and TCG are calculated for the whole design and used in the calculation of GZ. Conversions are performed automatically. fluid simulation is used for analyses that use a loadcase.Chapter 3 Using Hydromax
Fluid analysis method: Simulate fluid movement
This method is a faithful simulation of the static movement of the centre of gravity of the fluid in each tank. the actual fluid level in the tank. Specific gravity is calculated relative to a fluid having a density of 1000. The new LCG. Every tank is rotated to the heel and trim angle being analysed.

7499 6D00FF00FF00 6D006D00FF00 FF005F005F00 FF005B00FF00 6D00FF006D00 7F007F007F00 3F003F003F00 FF0000007F00
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.8400 0. There is one row for each of the 18 fluid types.0250 1. The densities file may be edited manually if desired. cannot be changed (any changes made will be ignored).9200 0. Tanks that have been specified as containing one of these fluids will be updated automatically when the density of the fluid is changed in the Density dialog. These are fluid name. fluid code. This is the first fluid in the list printed in bold font.8883 0. each separated by a tab character. blue components and are probably much more easily edited in the Density dialog. The name and code for the first entry. If the vessel is to float in a different fluid. Note that only the custom fluids may have their names changed. you would change the density of "Sea Water" to 1000. it is necessary to change the density of this fluid.9443 0. Note The vessel's hydrostatics are always calculated assuming the vessel is floating in the fluid labelled "Sea Water".0000 0. Thus. green.0250 1. All other entries may be edited (the same restrictions area applied as when editing through the Density dialog).
Sea Water Water Ballast Fresh Water Diesel Fuel Oil Lube Oil ANS Crude Gasoline leaded S B W D F L C G 1.Chapter 3 Using Hydromax
By assigning a code to the fluid you can easily apply the fluid type in the Compartment Definitions table.
Saving and Loading Densities
Densities listed in the Density table can be saved and loaded using the File menu. Tank calibrations results and loading conditions will also be updated. if you wanted to carry out an analysis for a vessel in fresh water. Sea Water. colour respectively (the colour is in hexadecimal for the red. specific gravity. The four columns.0 kg/m3.

you can always reset the densities to their default values in the Densities dialog.8524 0.Chapter 3 Using Hydromax
Unlead. JFA MTBE Gasoil Slops Custom 1 Custom 2 Custom 3 Custom 4 Custom 5
U J M GO SL C1 C2 C3 C4 C5
0. the waveheight reduces linearly with wavelength given by the formula: Wave height = 0.9130 1. The wavelength defaults to the waterline length of the hull at the DWL.0000 1. or as a sinusoidal or trochoidal waveform. wave height and phase offset can be specified.0000
FF007F007F00 7F007F00FF00 F600FA00C900 FF00FF007F00 FF006F00FF00 D6000300D600 D600D6000300 0300D600D600 D60003000300 DF00DF00DF00
If you make an error.607 √ Wavelength [m] This is the metric equivalent of the US Naval standard wave height: Wave height [ft] = 1. If the wavelength is modified the wave height defaults to a value in metres of: Wave height [m] = 0. select the Waveform command from the Analysis menu:
The water plane can be specified as flat.0000 1.7499 0.7471 0.0000 1. Gas.1 √ Wavelength [ft] For short waves of wavelength less than 64m.075875 Wavelength
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. the wavelength.0000 1. To specify a waveform.8203 0. Also see: Windows Registry on page 16
Waveform
Hydromax is capable of analysing hydrostatics and stability in arbitrary waveforms as well as for a level water plane. If a waveform is specified.

with a wavelength equal to the waterline length. whilst GMt and GMl are the actual vertical separation of the metacentres above the centre of gravity in the trimmed reference frame normal to the sea surface. the wave height may be modified. a phase offset of 0. Remember that KG is measured in the upright vessel reference frame (normal to the baseline).Chapter 3 Using Hydromax
Once a wavelength has been set. as a proportion of the wavelength. For example. Damage can be specified concurrently with grounding. If the vessel touches one or both grounding points. The phase offset varies between 0 and 1. will give a single wave crest at amidships.
Grounding
Grounding is an additional analysis environment option for the Equilibrium or Longitudinal Strength analysis.
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. The value of KG. It is possible to specify grounding on one or two points of variable length. the sum of the buoyancy and the grounding reactions equals the loadcase displacement. The Equilibrium analysis will determine whether the hull is grounded or free floating and will trim the hull accordingly. this will be reflected in the results: The displacement column will show the total grounding reaction force in brackets. both of which correspond to a wave crest at the forward end of the DWL.5. GMt and GMl are all calculated to the effective centre of gravity. The phase offset governs the position of the wave crest aft of the forward end of the DWL.
The effective centre of gravity will be modified by the grounding reactions – a mass is effectively being removed from the vessel. this will bring the effective centres of gravity and the centre of buoyancy in line vertically.

Stability Criteria
Stability criteria may be seen as the “environment of authorities” that the ship will be deployed in. the second grounding point is the aft grounding point. When two grounding points are entered. The vessel is considered to pivot at the centre of the grounding point. the first point (edit boxes on the left) must refer to the forward grounding point. Also see: Damage Case Definition on page 71
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.
Damage
You can specify whether the model is to be analysed in intact or damaged condition using the Analysis Toolbar.e.Chapter 3 Using Hydromax
Note: Grounding points are considered to span the transverse extents of the hull and therefore constrain the heel to zero. the vessel will not be balanced in heel and the vessel will remain upright (zero heel) even if the transverse metacentric height is less than zero. For more information see Chapter 4 Stability Criteria starting at page 163.
Note: Fixed zero heel during grounding analysis The equilibrium analysis will only consider the longitudinal balance of moments. i. The length of the grounding points is only used when considering the load distribution for Longitudinal Strength analysis and not to determine the pivot point.

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.Chapter 3 Using Hydromax
Analysis Output
Hydromax will produce the following output data:
Hydromax model visualisation Result data tables per analysis Graphs per analysis Report o o o Report window Streamed directly to a Word document Report Templates
In this section:
Reporting Copying Select View from Analysis Data Saving the Hydromax Design Exporting
Reporting
Hydromax has several options to do your reporting:
Batch Analysis text file and/or streaming to Report window Automatically generate a report in the Report Window for each analysis run Automatically Streaming results to Word Manually copy and paste tables and graphs from the Results Window and Graph Window
The most efficient method depends on the number of loadcases and damage cases you have to analyse and the output you require. After you have run an analysis a Word document is created and opened automatically. Additionally. Batch Analysis results saved as text files do not include graphs. if the option to Stream the report to Word has been selected in the Edit | Preferences dialog a word document is automatically generated after a Batch Analysis. For large numbers of cases. To do this:
Edit | Preferences Select the option to Send the Report to Word
This will send the Report document to Word instead of to the Report window. Select the option to send the results to the report window if you require Graphs. This also applies to Batch Analysis.
Streaming results to Word
It is possible to stream the Analysis results directly to Word. Form small number of loadcases and damage cases you can do a manual copy and paste of the results into a report. it is recommended to use batch analysis. This then allows you to validate the results at the same time.

Simply tick the box „Use Word Templating‟.dotx/dotm (for Word 2007) format and will be used when creating any future reports. To turn on Report Templating you need to select it in the Preferences dialog box. Please note that Send Report to Word must be enabled before you can enable this option. it is possible to use template keywords to specify where in the document the analysis results go and where each element of the output (such as graph. See the dialog box below as an example:
The Word Template File specified should be in . Two Report Templates have been included to get you started: StabilityBooklet. This feature is only available when sending reports to Microsoft Word. etc) is placed. With report templates. You can use one of the sample templates provided.dot or . or you can build your own template.dot
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. This gives you much greater control over how the analysis results are output than with the normal Send Report to Word option and allows you to customise your own report template document. tables.Chapter 3 Using Hydromax
Report Templates
Hydromax offers the ability to customise reports through a Report Template. instead of just dumping the results of each analysis into a Word document.

These allow you to easily add and remove the analysis keyword blocks.
The location of these report templates varies depending on which operating system you are using. Simply double-clicking on a template document opens up a new document based on the template (which is not what you want). Users can start with StabilityBootlet.
Copying Hull Views
Pictures of the hull in the View windows may be copied to the Clipboard using the Copy command from the Edit menu. It contains an introduction to how templates are created and configured. On Windows XP/Server 2003 the default location for the report templates is: C:\Program Files\Maxsurf 14\Report Templates\ On Windows Vista.
Copying & Printing
A range of options for transferring data from Hydromax to other programs such as spreadsheets and word processors is provided through copy and paste functions. It also includes all of the basic analysis blocks and variables to get you started. due to new security changes we‟ve had to move this to an alternative location that every user has write access to – so you can find it at: C:\Users\Public\Documents\Maxsurf\Maxsurf14\Report Templates\
Tips:
See: Copying Tables on page 158 for tips on how to include the table header in a copy paste to for example Excel Graph Formatting on page 190 for tips on how to format your graph prior to copying to another application. HMReportTemplate. Data Format on page 207 for tips on how to specify what should be displayed and customise how to display tables (vertical or horizontal).
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.dot and then use it customise their own report template.g. copying and pasting data to and from Excel spreadsheets allows you to use the full spreadsheet capabilities of Excel on your Hydromax model.dot This document is a good starting point for creating your own customised template. This data transfer works both ways: e.
Note: To edit a report template in Microsoft Word you will need to start Microsoft Word and then open the template directly using the File menu. Both of these templates contain macros and toolbar items to make life easier when you design your own template. The image copied is as per the image displayed in the Hydromax view window.Chapter 3 Using Hydromax
This is an example of a complete Stability Booklet template – this document is the default Word Template file for new users and is recommend for users wanting to quickly create a Stability Booklet.

it is possible to ensure that the graph is plotted to a sensible scale so that measurements can be made directly from the graph. then the graph will be plotted so that the grid lines are at one of the following intervals (If the current length units are imperial then similar intervals will be used.5cm. Choose the Colours button and select the options required. range of cells or the whole table and then choose the Copy command or Ctrl+C.0cm. Prior to printing you may wish to set up the paper size and orientation by using the Page Setup command from the File menu. To copy a simple bitmap image of the view at the current resolution. If these are metric. To do this. additionally. will also copy the column headings. Simply select a cell.
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. column. The printing may be forced to be black and white. Simply bring the window you wish to print to the front and choose Print from the File menu. row. You will be asked if you want to print the graph to scale or to fill the page:
The scale used will depend on the length units that are currently selected. otherwise click the Cancel button. To print the page click the Print button. The titles may be edited by clicking the Titles button. 5. but they will be inches instead of cm.
Graph Printing to Scale
When printing the graph. use Ctrl+I. 2. but the selection will be reflected in the printout. Views of the hull in the View window may be printed to scale as in Maxsurf. The data copied from the table will be placed on the clipboard and can then be pasted into a spreadsheet or word processor for further work. 2. Note: Copying data from the table with the Shift key depressed.
Printing
Each of the windows in Hydromax may be printed.0cm. hold the shift key down when selecting the print command for the graph.
Print Preview
The page to be printed is initially displayed in print preview mode.): 1. a bitmap of the current image may be saved by pressing Ctrl+Shift+I
Copying Tables
Tables may be copied to the clipboard.0cm. Note that the print preview is not refreshed after these changes.Chapter 3 Using Hydromax
These pictures can then be pasted into other applications or the Hydromax Report window.

g.hmd file with the same name as the design.
Saving Input Files separately
In addition to saving all the data together. key points etc. compartment definition. For example: the angle of downflooding can be visualised by returning to the Stability table in the results window. ensure that the View window is topmost and select Save from the File menu. each step from the analysis can be visualised when the analysis has completed.
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.. The Hydromax data is saved in a . This gives the option of loading common data into different design files. For more information on file properties and extensions in Hydromax.hmd file automatically every time you press Save from any of the design windows. E.
Select View from Analysis Data
For most analyses.
Saving the Hydromax Design
Hydromax design data may be saved
Saving in a Hydromax Design File Saving Input Files separately
Saving in a Hydromax Design File
To save the design in one file. The Select View from Data can also be used to display the Curve of Areas graph for each intermediate analysis stage. the data in the individual tables such as loadcases. see Graph type on page 189. may also be saved separately. for comparing the characteristics of vessels which have only minor differences in hull shape and identical tank layouts and loadcases. selecting the column at the required heel angle and select “Select View From Data” in the Display menu.
In the View window the hull will be displayed in the selected position. Note Although all Hydromax model data is saved in the . it is recommended to also save the Hydromax input files separately. damage cases.Chapter 3 Using Hydromax
Exporting a Bitmap Image
You may also export a bitmap of the rendered perspective view with the File | Export | Bitmap Image command. This can also be done for Upright Hydrostatics and the different wave phase calculations for an Equilibrium analysis in a waveform. please see: File Extension Reference Table on page 307.

To save the loadcase table. Selecting this option saves all the loads displayed in the current tab in the Loadcase window.
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. This allows the same loading spreadsheet to be recalled at any time for use with the same design or with any other hull. Saving Damage Cases to a File Bring the Damage window to the front and select Save Damage Cases or Save Damage Cases As from the file menu. select Save Compartment Definition from the File menu. You will be asked to name the file and select where it is to be saved. select Save from the File menu. meaning that they can be read directly into spreadsheets such as Excel with values being placed in individual spreadsheet cells. Saving Compartment Definitions to a File To save a compartment definition to a file. you can save it in a file on disk. ensure the Results window is topmost on the screen and choose the table containing the data you wish to save. bring the Input window to the front and choose the compartment definition table.
Exporting
The data export function in Hydromax is similar to Maxsurf. You will be asked to name the file and select where it is to be saved. the data generated may be saved as a text file.
Saving Results to a File
Once you have performed an analysis. The Results files are saved as tab delimited text. Saving Input Window Tables To save a input window table to a file. Selecting this option saves all the data currently displayed in the Results window. ensure the Loadcase window is topmost on the screen and choose Save Load Case from the File Menu. This allows for further calculations to be done in a spreadsheet or for formatting to be done in Word. To save the data. Some Hydromax-specific export features are described below. Excel or other programs. Select Save or Save As from the File Menu. bring the Input window to the front and choose the required input table.Chapter 3 Using Hydromax
Saving Loadcases to a File Once you have set up a loading spreadsheet.

Hydromax models created in versions greater than version 8.
Exporting the Model to Hydromax Version 8. so it is important to have unique compartment names.
DXF export Contains all lines displayed in the active design window as closed poly-lines. For more information on data export of DXF and IGES.0 can be exported using the File | Export menu so that it is compatible with Hydromax version 8. In addition. This export function is particularly useful to export tank arrangement drawings. Note: The layer name is the same as the compartment name. each tank. All key points will become downflooding points in the version 8 file and any tank sounding pipe information will be lost.0
After Hydromax version 8.
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. compartment and non-buoyant volume is exported on a separate layer.Chapter 3 Using Hydromax
Data export dialog in Hydromax. a major change to the Hydromax file structure was made.0. please see the “Output of Data” section in the Maxsurf manual.

.

Although all criteria are displayed in the criteria table. Hydromax uses a single dialog to control all the stability criteria. only the applicable criteria are added to the report (although all are displayed in the Results table). Stability criteria are evaluated for Large Angle Stability. i. Criteria Results. simplified dialog. This section describes how this list of criteria can be divided up in to Parent heeling arms. predefined custom criteria and user created custom criteria.
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. Parent criteria. only criteria that are applicable are added to the report. These custom criteria files may be easily transferred via email. The following sections will be discussed:
Criteria Concepts. explanation how to work with the Hydromax criteria dialog to create your own custom set of criteria. an overview of what capabilities Hydromax offers with regards to stability criteria. ISO and more. A fixed sub-set of criteria is used for the Floodable length analysis and these criteria are accessed in their own. Equilibrium and Limiting KG calculations. HSC. This makes it quick and easy to set which criteria should be included for analysis and to change criteria parameters. These criteria are listed using in a tree control on the left-hand side of the criteria dialog. Criteria Procedures.e.e. DNV. Help information relating to the use and parameters of each criterion is displayed in the lower right hand corner of the dialog. criteria evaluation results Nomenclature. only the criteria that are selected for evaluation during an intact analysis will be evaluated and added to the report. It is also possible for users to create their own custom sets of criteria. explanation of terms and definitions
See also:
Appendix B: Criteria file format Appendix C: Criteria Help Appendix D: Specific Criteria
Criteria Concepts
Hydromax includes a wide range of template criteria (or: parent criteria) as well as predefined custom criteria such as IMO. i. Criteria may be identified as intact or damage criteria (or both). and after a Large Angle Stability analysis only GZ based criteria are added to the report.
Criteria List Overview
Hydromax includes a wide range of criteria. after an Equilibrium analysis only those criteria that are evaluated from Equilibrium data are added. Criteria results are added to the Report after a Large Angle Stability or Equilibrium analysis.Chapter 4 Stability Criteria
Chapter 4 Stability Criteria
This chapter describes how stability criteria are used in Hydromax. import and edit their criteria sets. This section also explains how all criteria can be divided up into two different criteria types: equilibrium and GZ curve based.: if the intact case is being computed. Users may save. similarly for the damage cases. However. This ensures that the correct criteria are evaluated and displayed during normal and batch analysis.

for example.
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. Those heeling moment are then used in a number of different criteria. the roll-back angle required for the IMO IS code Severe wind and rolling (weather) criterion. The Hydromax criteria list contains Parent Heeling Arms that can be copied into a custom criteria folder and then cross-referenced into the stability criteria.Chapter 4 Stability Criteria
The criteria tree list
Parent Calculations This folder contains calculations that are required for certain criteria parameters. These calculations may be referenced in certain criteria.
Parent calculations in Hydromax Criteria dialog
Parent Heeling Arms In most cases a ship is subject to specific heeling moments.

This is because the parent criteria are intended for use as templates from which you can derive your own custom criteria. Parent Criteria The Parent Criteria group contains all the parent criteria types that are available in Hydromax. To distinguish the Parent criteria from your derived criteria. those that are not locked require your ship design data to be input. This folder can be found in the Maxsurf root directory: c:\program files\Maxsurf. Another benefit is that. These may be found in the “HMSpecificCriteria” folder.Chapter 4 Stability Criteria
The advantage of using cross-referenced Heeling Arms is that a heeling arm is now defined (and edited) in only one place. Custom Criteria You can create your own set of criteria in the tree as well. Also the parent criteria settings cannot be saved. since the heeling arm is defined in one place. This is explained in the section on Working with Criteria on page 168. This ensures that all criteria which use a specific heeling arm use exactly the same heeling arm. Each parent criterion allows you to perform a specific calculation. Predefined Custom Criteria A number of criteria files containing criteria for specific codes are supplied with Hydromax. This is done by dragging the required parent criteria in to the “My custom criteria” group or any other group you create. delete or add criteria to the Parent Criteria group. they will always revert to their default values when Hydromax is restarted. Most specific criteria are locked. Also see Working with Criteria Libraries on page 172 Appendix D: Specific Criteriaon page 291. they are displayed in bold text in the Criteria list.
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. Parent criteria are special in that you cannot rename. it is only displayed once in the GZ graph and not duplicated for each criterion that uses it. Furthermore some newer heeling arm criteria are only available for cross-referenced heeling arms and a greater variety of heeling arm definitions are available through cross-referencing. these are the fundamental criteria from which criteria for specific codes are derived.

Equilibrium criteria can be recognised by the icon. freeboard measurements. A check is also made to ensure that any selected Equilibrium criteria are passed. STIX. These icons are derived from the parent criterion type. For this reason. These are calculated after a Large Angle Stability analysis and during a Limiting KG analysis. These criteria perform several individual tests on the GZ curve including a heeling arm. These criteria are evaluated only after an equilibrium analysis has been performed. once in the form of an Equilibrium criterion and again as a Large Angle Stability criterion. GZ criterion. in some criteria sets some criteria are included twice. The different types of criteria and their icons are described below: Folder icon. These criteria make measurements from the GZ curved obtained from a Large Angle Stability analysis. Weather criterion. angle of maximum GZ. The same also applies for GMt. etc. These criteria perform several individual tests on the GZ curve. GZ area criterion GZ criterion with heeling arm GZ area criterion with heeling arm GZ criterion with several heeling arms and their combinations GZ area criterion with several heeling arms and their combinations Combined GZ criterion. Combined GZ heeling arm criterion. This type of criterion is also used by the Floodable Length analysis. For example.g.Chapter 4 Stability Criteria
Types of criteria
There are two fundamental types of criteria: Equilibrium criteria Equilibrium criteria are evaluated after an Equilibrium analysis and refer only to the condition of the vessel in its equilibrium state For example: margin line immersion tests. area under GZ curve between specified limits. etc. notably angle of equilibrium heel. These criteria are often referred to as Large Angle Stability (LAS) or GZ criteria. create separate folders to store related criteria. See next: Criteria Procedures
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. Note that there is some cross-over between the criteria types. but they cannot be included directly in the search algorithm. The equilibrium heel angle is also a fundamental output of the Equilibrium analysis. it must be a LAS criterion. metacentric height. Criteria derived from measurements of the GZ curve.g. This is because it is only this type of criteria that is more likely to pass as VCG is reduced. trim angle. e. For a criterion to be used in the search for maximum VCG in the Limiting KG analysis. This can be measured from the GZ curve by looking for an up-crossing of the GZ=0 axis. Equilibrium criterion. You will notice that different icons are used to differentiate between different types of criteria. e. All folders must have unique names (even if the parent folders have different names).

To bring up the Criteria dialog. in the analysis toolbar:
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Starting the Criteria dialog Resizing the Criteria dialog Working with Criteria Editing Criteria Working with Criteria Libraries
Starting the Criteria dialog
The criteria dialog allows you to select which criteria are selected for inclusion in the analysis and change their parameters. select Criteria from the Analysis menu:
or use the Criteria button.Chapter 4 Stability Criteria
Criteria Procedures
This section describes how to work with the stability criteria dialog.
.

The criteria command will bring up the Floodable Length Criteria dialog when the Floodable Length analysis is selected.
Resizing the Criteria dialog
The dialog may be resized and a vertical and horizontal slider can be used to resize the width of the Criteria List and the height of the Criterion Details areas. This section explains how to create and customise your own criteria from the Parent Heeling Arms and Criteria provided with Hydromax.Chapter 4 Stability Criteria
The criteria dialog is shown below:
Note: The Floodable Length analysis uses its own set of criteria. the dialog size can be reset by holding down the “Shift” key when you open the dialog.
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Working with Criteria
In the Concepts section it was explained how the criteria are listed in a tree list. in the unlikely event that the dialog items vanish due to resizing the dialog. This behaviour is the same as all other resizing dialogs. Note that if.

Click on an item’s name or icon to select it Once selected.Chapter 4 Stability Criteria
Using the Criteria Tree List
The tree works in much the same way as the file folders in Windows Explorer:
   
Click on the “+” sign to expand the folder (or double click on it). Click on the “-” sign to collapse the group (or double click on it). this prevents inadvertent editing of its parameters. If a criterion is locked. Lock: Toggle whether the criterion (or all criteria within the group) are locked. click again on the on the item’s name to edit its name
Some short-cut keys for the tree list: Tree control smart keys Alt+Keypad * Right Arrow or Alt+Keypad + Left Arrow or Alt+ Keypad Up Arrow Down Arrow Space
Criteria Tree Right-click Context Menu
Function Recursively expands the current group completely Expands the current group Collapses the current group Move one item up tree Move one item down tree Include criterion for analysis
Several options are available by right-clicking on a criterion or criterion group:
Criterion right-click menu
Include for Analysis: Toggle whether the criterion (or all criteria within the group) should be evaluated. Intact: Toggle whether the criterion (or all criteria within the group) should be evaluated for intact conditions. Locking is used for criteria belonging to specific codes where the required values are fixed. Damage: Toggle whether the criterion (or all criteria within the group) should be evaluated for damaged conditions.
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all criteria that should be in a group of that name will end up in the first one and none in the second.
Copying criteria
You can use the Criteria Tree Right-click Context Menu to copy and paste criteria.
Defining new Custom Criteria and Groups
New custom criteria sets may be created by first creating a new criterion group and then dragging the desired criteria into the criterion group. By holding down the Ctrl button a copy of the criterion being dragged is created (unless it is a parent criterion. If there are groups with the same name. you can hold down the CTRL-key while moving the criteria you will copy the criteria. then clicking again in the label.
Moving Criteria
Criteria may be moved from one group to another by dragging them with the left-mousebutton or by using the cut and paste functions in the right-click context menu (see above). Copy: Copy the criterion (or whole criterion group) to the clipboard. This may then be pasted into another location in the tree. Alternatively use the Copy and Paste functions from the right-click context menu (see above). Delete: Deletes the criterion or all the criteria and sub-groups within the group. As criteria (and new groups) are loaded they are inserted into the first group that is found with a name that matches the name of the group to which the criterion should belong.
Editing Criteria
The specific details for a criterion are displayed in the table in the top-right of the dialog:
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. This may then be pasted into another location in the tree. right-click on the group and choose Include for Analysis from the menu.
Selecting the Criteria for Analysis
Criteria may be selected for analysis by ticking the tick box to the left of the criterion. Alternatively. Note that if you drag a criterion from the Parent Criteria group a copy will be made and the original will not be deleted. in which case a copy will be made regardless of whether the Ctrl key is held down or not). If duplicate group names exit. Paste: Paste the criterion (or whole criterion group) from the clipboard to the selected location Rename: Renames the criterion or group. Cut: Cut the criterion (or whole criterion group) to the clipboard. To select an entire group. It is extremely important to ensure that all criteria groups have unique names. Other functions are available from a menu activated when the right button is clicked on your mouse. then loading the criteria file may cause unexpected results.Chapter 4 Stability Criteria
Add Group: Add a new criterion group. This may also be done by selecting the label.

have a grey background. If in doubt. where the items are mutually exclusive. Edit the parameters as required and then select the next criterion to be edited from the tree. the check boxes act as radio buttons and only one may be selected. use the File | Save Criteria command to save a copy of your current criteria selection and data before making any changes in the Criteria dialog.Chapter 4 Stability Criteria
Criterion details table
To edit the parameters for a specific criterion. For example the limits for an upper integration range or the individual criteria to be evaluated for a more complex criterion:
In both of these cases the selection is cumulative and none of the selections are mutually exclusive. at least one must be selected. In most cases there will be group of related options used to define a criterion parameter.
Check Boxes in Criteria Properties Section of Criteria Dialog
There is some subtly different behaviour for the check boxes in the dialog depending on their context. those which cannot be edited. The values that are required for passing a criterion are in bold. This occurs. The parameters that may be adjusted have a white background. click on the criterion‟s name in the tree and the criterion‟s parameters will be displayed in the table on the right. with the “Value of GMt at” criterion:
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In other cases. or click the dialog‟s Close button. However. for example. Please note that the criteria are updated as you change their data and that there is no “Cancel” function for this dialog.

for example. only the criteria that you create or import will be saved. Criteria that are defined for both are always evaluated. Hydromax allows you to make this distinction by selecting the required comparison from a combo-box in the criterion row of the details table:
Description Shall be greater than Shall not be less than Shall be less than Shall not be greater than
Damage and Intact
Symbol > ≥ < ≤
Logical test Greater than Greater than or equal to Less than Less than or equal to
Criteria may be defined as intact or damage stability criteria (or both).hcr” from the directory in which the Hydromax program resides. GZ curve reduction in the wind heeling criteria:
Criterion Pass/Fail Test
There are some subtle differences between the wordings for different criteria.
Default Criteria Library File
When starting.Chapter 4 Stability Criteria
Finally a check box can be used to select whether a specific effect should be included. which consists of the Parent criteria and a “My Custom Criteria” group.
Working with Criteria Libraries
It is possible to load and save the criteria.
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. Intact criteria are only evaluated for the intact case and damage criteria are evaluated when a damage case has been selected (irrespective of whether there are actually any damaged compartments or tanks in the damage case). whereas another may state “Shall not be less than…”. The parent criteria.hcr. For example one criterion may state “Shall be greater than…”. By default this is c:\program files\Maxsurf\ Hydromax Criteria Library. you will be prompted to locate a criteria file: You may select an alternative file or click the Cancel button to proceed and be given the default criteria. A third option which is not yet implemented is WOD (Water on deck) this checkbox has no effect. These options may either be set using the right-click menu or by ticking the appropriate boxes in the bottom of the dialog:
Intact and Damage tick-boxes. If this file cannot be found. built into Hydromax are not saved. Hydromax will try to open the default criteria library file called: “Hydromax Criteria Library.

the imported criteria will be found in the original groups. This will simply export all the custom criteria (parent criteria are not saved) to the specified file. Note It is good practise to save the criteria file with the project in the project folder. A number of criteria containing criteria for specific codes are supplied with Hydromax. it is important to ensure that the group names in the file you are importing are not the same as those that already exist. updates will be saved in the default criteria library. Note that when keeping your existing criteria. all criteria are still available. Further updates will. Even if you loaded an alternative file. either overwriting the existing one or creating a new one. These may be found in the “HMSpecificCriteria” folder. This can be useful when you are defining new custom sets of criteria that you wish to keep separate or when defining criteria sets for different vessels. all existing criteria except the parent criteria will be removed and replaced by those in the file you are opening. The default criteria library will be over-written with the new criteria so if you wish to keep any custom criteria that you may have added to your default criteria library. or Ctrl select to select multiple files in the Open Hydromax Criteria dialog. Choose Save Criteria As from the File menu. See Saving Criteria below. you must save them in a new file first. when at a later stage you need to re-analyse the project. You can import several criteria files in one go using Shift.
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. however.
Saving Criteria
It is also possible to save the criteria into a new file. if you choose “No”.
Importing Criteria and Specific Criteria Files
New criteria may be added to your criteria list by importing them – choose Import Criteria from the File menu. continue to be saved to the default criteria library file that was opened when Hydromax was first started. You will then be asked if you wish to keep the existing criteria:
If you choose “Yes” your existing criteria will be kept. so if you want to save any further changes you will have to resave as described above. If this does occur. That way. not in the new groups.Chapter 4 Stability Criteria
The default criteria library will be automatically updated every time the criteria dialog is closed.

This is normally due to an insufficient range of heel angle having been used. Editing this file will also allow you to add your own help text or associate rich text format help files (rtf) files with your criteria. The format for the results table and the report are specified separately.. e. Intermediate values are displayed.html. angle of equilibrium. criteria are evaluated and the results displayed in the Stability Criteria table in the Results window. Results may be displayed in “Verbose” or “Compact” format (see above).hcr.g. Values that could not be calculated. The file is a normal PC text file. which may be edited manually so as to generate custom criteria.: angle of vanishing stability. Criteria can also be re-evaluated without having to redo the analysis when “Close and Recalculate” is selected in the criteria dialog.
Criteria Results
After a Large Angle Stability or Equilibrium analysis. The typical format of the file is given in the following file: c:\Program Files\Maxsurf\\HMCriteriaHelp\CriteriaHelp.
Criteria Results Table
The tested criteria are listed one above the other. have n/a in the Actual and/or Value column. This allows you to edit criteria parameters or selected criteria and re-evaluate using the existing analysis results. etc. Chose the Display | Data Format command when the Stability Criteria results are displayed:
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. After calculation the relevant criteria are also added to the Report.Chapter 4 Stability Criteria
Criteria File Format
The criteria are saved in a Hydromax criteria file with the extension .

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. Also see Reporting on page 155 Batch Analysis on page 138
Nomenclature
This section gives a brief description of the various values that are determined by Hydromax in the evaluation of criteria.e. For example damage criteria during intact analysis or Equilibrium criteria during a Large Angle Stability analysis are not added to the report.e. trim angle. only the relevant criteria results are added to the Report and/or Batch file. freeboard measurements. Criteria derived from measurements of the GZ curve. any criteria that have a “not analysed” result. etc.
Definitions of GZ curve features
Some typical GZ curves are shown below. For example. Note: The metacentre is always (even for Large Angle Stability criteria) computed directly from the vessel‟s hydrostatic properties (i. Criteria that are not relevant. angle of maximum GZ. area under GZ curve between specified limits. i. are not added to the Report (although they are displayed in the Criteria Results table). metacentric height. This type of criterion is also used by the Floodable Length analysis. This gives an accurate result that is not dependent on the heel angles and intervals tested during the analysis. There are two distinct types of criteria: Equilibrium criteria Equilibrium criteria are evaluated after an Equilibrium analysis and refer only to the condition of the vessel in its equilibrium state For example: margin line immersion tests.Chapter 4 Stability Criteria
Report and Batch Processing
As noted earlier. Equilibrium criteria can be recognised by the icon. water-plane inertia and immersed volume) at the specified heel angle and not from the slope of the GZ curve. These are calculated after a Large Angle Stability analysis and during a Limiting KG analysis. These criteria are often referred to as Large Angle Stability (LAS) or GZ criteria. etc. the third graph shows the GZ curve with a heeling arm overlayed.

The angle of vanishing stability with a given heeling arm is the smallest positive angle where the GZ curve crosses the heel arm curve and where the GZ-Heel Arm curve has negative slope.Chapter 4 Stability Criteria
GZ curve with heeling arm superimposed GZ Definitions
The table below defines how Hydromax calculates the various features of the GZ curve: Angle of vanishing stability Angle of vanishing stability with heeling arm curve Downflooding angle Equilibrium angle Equilibrium angle with heeling arm curve First peak in GZ curve The angle of vanishing stability is the smallest positive angle where the GZ curve crosses the GZ=0 axis with negative slope. The equilibrium angle with a given heeling arm is the angle closest to zero where the GZ curve crosses the heel arm curve where the GZ-Heel Arm curve has positive slope. this often occurs if the vessel has a large watertight cabin. The downflooding angle is the smallest positive angle at which a downflooding point becomes immersed. the GZ curve may have multiple peaks. In some cases.
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. The angle of the first peak is the lowest positive angle at which a local maximum in the GZ curve occurs. The equilibrium angle is the angle closest to zero where the GZ curve crosses the GZ=0 axis with positive slope.

combined effect of heel and trim. These include the effects of wind. rotated to the specified heel (and trim) angle. If a criterion uses a roll back angle. Depending on the moment that they represent. the Gust Ratio is the ratio of the magnitude of the gust wind heeling arm to the steady wind heeling arm. the heeling arm is made zero. This is typically used to assess the effects of external heeling moments. which are applied to the vessel. i.80665ms-2 Roll back angle The maximum slope of an initially horizontal. The heeling arms are never allowed to be negative. it is often necessary to calculate the GZ curve for negative angles of heel. Commonly used in wind and weather criteria to account for the action of waves rolling the vessel into the wind. the heeling arm is forced to be zero at heel angles greater than 90° and less than -90°. etc. the resulting heel angle after the roll back has been applied is more negative than the original. If the heeling arm has a power of cos greater than zero. Used for some wind heeling criteria. Note that the centre of gravity used is the upright centre of gravity corrected by the free surface moments of partially filled tanks in their upright condition. if the cos function goes negative. passenger crowding. Often a roll back angle is measured from some equilibrium position.
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. centripetal effects of tuning.e. Positive angle at which the value of GZ is a maximum Positive angle at which the value of (GZ . flat deck at the resultant vessel heel and trim. the heeling arm curves will have different shapes. The location of the metacentre is computed from the water-plane inertia. 1998 CODATA recommended value for standard acceleration of gravity A negative heel angle change. which is superimposed on the GZ curve. not the slope of the GZ curve.Chapter 4 Stability Criteria
GML or GMT
GZ Curve Heeling arm curve
Vertical separation of the longitudinal or transverse metacentre and centre of gravity. The curve of vessel righting arm (GZ) plotted against vessel heel angle A curve of heeling lever.heel arm) is a maximum
Maximum GZ Maximum GZ above heeling arm curve
Glossary
The table below describes some commonly used terms: Angle of heel measured from upright. Deck Slope / maximum slope Gust Ratio g = 9.

An assembly view has been added to Hydromax, this makes it easier to control the visibility of individual tanks and surfaces. The Properties sheet can be used to change tank properties of the tank currently selected in the Assembly or design View.
View Window

The View window displays the hull, frame of reference, immersed sections of the hull and any compartments, and the centroids of gravity, buoyancy, and flotation. These positions are represented by: cb cg cf K centre of buoyancy centre of gravity centre of flotation location of keel (K) for KN during KN analysis

You can choose which type of view is displayed by selecting from the Window menu or the View toolbar. The Zoom, Shrink, Pan and Home View commands from the View menu may be used and work in exactly the same way as in Maxsurf. If a Perspective view is shown, you may also use the Pitch, Roll and Yaw indicators to change the angle of view. Please refer to the Maxsurf manual if you are unfamiliar with these functions. You may set the visibility of the various display elements by using the Visibility command from the Display menu. Two sets of visibility flags are maintained, one is used for all analyses other than tank calibration and the other is used for when the tank calibration analysis is selected.
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If a view window is visible when an analysis is being carried out, it will display the hull shape using the correct heel trim and immersion for the current step of the analysis. After an analysis, the Select View from Data command in the Display menu may be used to move the hull to a selected position from the Results window. The view of the tanks, compartments and non-buoyant volumes can be toggled between an outline view and a view of the sections.
Perspective view

In the perspective view, the model may be rendered.

The rendered view also enables tanks and compartments to be more easily visualised, especially when the hull shell is made transparent.

The rendering options are to be found in the Display menu, with further lighting options in the Render toolbar. Please refer to the Maxsurf manual for more information on the different rendering options available in perspective view.

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Note: Fastest performance will be achieved by reducing the amount of redrawing that is required from Hydromax. For this reason, it is best to turn off sections, and especially waterlines, when performing an analysis. You may then turn them on again after the analysis has completed. For fastest performance, e.g. when running in Batch mode, minimise the Hydromax window so that no redrawing occurs.

Loadcase Window

In the Loadcase window a spreadsheet table of all loads and tanks is displayed.

Using the tabs on the bottom of the window allow you to quickly browse through the different loadcases. Hydromax allows you to improve the presentation of the Load Case window by adding blank, heading or sub-total lines in the table. For more information see Working with Loadcases on page 38. The columns that are displayed may be selected using the Display | Data Format dialog.
Damage Window

The Damage window is used to specify which tanks and compartments are flooded in each damage case. There is always an Intact case, which cannot be edited, this is the default condition. If flooded volumes are required in the intact case they should be defined as non-buoyant volumes.

The input window contains tabs on the bottom that allow you to quickly browse through the different input tables.
Compartment Definition

This table can be used to define the tanks and compartments in the Hydromax models. For more information see Modelling Compartments on page 51 in the Analysis Input section.
Sounding Pipes

This table is used to define the tank sounding pipes and calibration intervals. Default values are provided but these may be edited if necessary.

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Key Points

There are several types of Key Points:
Down Flooding points Potential Down flooding points Embarkation points Immersion Points

Only downflooding points are used in determining the downflooding angle, which is used in criteria evaluation.
Margin Line Points

The margin line is used in a number of the criteria. Hydromax automatically calculates the position of the margin line 76mm below the deck edge when the hull is first read in. If necessary, the points on the margin line may be edited manually in the Margin Line Points window (the deck edge is automatically updated so that it is kept 76mm above the margin line).
Modulus Points

This table is used to define the allowable limits for shear force and bending moment during the longitudinal strength calculations.
Bulkheads

See Floodable Length Bulkheads on page 77. Results Window

The Results window contains ten tables, one for each of the different analysis types plus criteria results and key points results tables. When switching mode, the currently selected results table will change to reflect the current analysis mode. Note that results are never invalidated if analysis options are modified – it is up to the user to ensure that the results are recalculated as necessary.
Setting the Data Format

It is possible to configure Hydromax so that only the results that you wish to see are displayed. To do this, choose Data Format from the Display menu.

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with Upright Hydrostatics. select Data Format from the Display menu. You may change the display format at any time after the analysis without having to redo the calculations. and select either the horizontal or vertical layout button. Equilibrium and Specified condition Analysis. Items that are selected with a tick will be displayed in the Results window and on any printed output.Chapter 5 Hydromax Reference
A dialog similar to the one above will appear. The data available for display depends on the analysis. or so that each draft is on a separate row. but are not displayed.
Key Points Data Result Window
Key points data is calculated for Large Angle Stability. The DF angle column is only visible when the analysis mode is set to Large Angle Stability and the Freeboard column is only displayed when the analysis mode is set to Equilibrium or Specified condition.
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. the data can be formatted so that each draft has a column of results. Items that are not selected are still calculated during the analysis cycle. For example.
To change the format.
Data Layout
Most analysis data can be formatted vertically or horizontally to fit better on the screen or the printed page.

where all the intermediate calculations are shown. the results can be displayed in verbose format.
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. Criteria results are not displayed in this table after a Limiting KG analysis. Limiting KG and Equilibrium analyses.Chapter 5 Hydromax Reference
Stability Criteria Result Window
If stability criteria are turned on in the analysis menu. they will be evaluated during Large Angle Stability. The results may be displayed in compact format:
Alternatively. by selecting the desired format in the Display | Data format dialog. The results of the criteria evaluation are presented in this table after Large Angle Stability and Equilibrium analyses.

Depending on the analysis mode.Chapter 5 Hydromax Reference
Graph Window
The Graph window displays graphs. Only the graphs that are applicable to the current analysis can be displayed. Upright Hydrostatics Analysis:
Hydrostatics Curves of Form Curve of areas – different graph for each draft tested (selected using Display|Select view from data)
Large angle stability Analysis
Righting Lever (GZ) Curve of areas – different graph for each heel angle tested (selected using Display|Select view from data) Max steady heel angle Large angle stability (hydrostatic data other than GZ) Curves of Form Dynamic stability (GZ area)
Equilibrium Analysis:
Curve of areas
Specified condition Analysis:
Curve of areas
KN Values Analysis:
Cross curves (KN)
Limiting KG Analysis:
Limiting KG
Floodable length Analysis:
Floodable length
Longitudinal strength Analysis:
Longitudinal strength Curve of areas
Tank Calibration
One graph for each tank
For many graphs you can select what is plotted and other options with the Display | Data Format dialog. Hydromax will automatically display the graph that displays the result of the current analysis when you select Graph from the Windows menu or press the toolbar button. Alternatively you can select a specific graph using the Windows | Graphs menu item. Graphs can be copied using the Edit | Copy command.
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. different graphs are available. which show the results of the current analysis.

the area is always given in units of length. Area and corresponding heel angle can be measured by using the slider.radians. These graphs include Upright Hydrostatics. These can all be displayed via the Graphs item in the Windows menu.degrees and cannot be displayed in units of length. use the mouse to click anywhere on the curve.
GZ Graph
The GZ value. Floodable Length and Tank Capacities. Note: Because the horizontal axis scale is always in degrees.Chapter 5 Hydromax Reference
Graph type
Hydromax can graph many types of data depending on the type of analysis being performed. the slider data is displayed at the bottom of the Graph window.
Interpolating Graph Data
To display an interpolated value from one of the curves. Click anywhere on the dashed line and drag it with the mouse. The data in the lower left corner of the window will change to display the curve name and co-ordinates of the mouse on the curve. Righting Lever (GZ curve). Hydromax will ignore the exact position you click on the curve to allow reading all related interpolated values along the black dashed line. Curves of Form. The area is integrated from zero heel angle to the location of the graph slider.
Note: In case multiple curves are plotted in the same graph you can switch between the curves by clicking on them. Tip: You can use the Select View from Analysis Data option (page 159) to see the Curve of Areas for each heel angle and/or intermediate stage during the analysis. Longitudinal Strength. as you move the cursor the interpolated values will be displayed.
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. Curve of Areas.

The View | Font command allows you to change the text size and font size. This ensures that the fitted line goes exactly through the calculated GZ points. Thus if you require the area between two limits. add a heel angle interval of greater than 10˚ as the final step. Since the graph data contains more data points than most tables in the results window. Note that the picture is placed in the clipboard as a meta-file which can be resized in Word or Excel. Especially in the case of the sectional area curve.
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. this double click can be extremely helpful to export the analysis data to for example Excel fro further processing. where there is no tabular data available. you must subtract the area at the lower limit from the area at the higher limit. If this is the case.
Curve fitting for GZ graph
A curve fit will be performed if all the heel angle intervals are less than or equal to 10˚.
Graph Formatting
When you are in the Graph window you can use the View | Colours and lines dialog to change the colours of the curves in the graph as well as the background.
Graph data
The graphed data can be obtained by double clicking on the graph. a parametric cubic spline is used to fit a smooth curve through the calculated GZ data at the specified heel angles.
Copying Graphs
You can copy the contents of the Graph window using the Copy command or Ctrl+C. This can sometimes be useful if you expect a discontinuity in the GZ curve.Chapter 5 Hydromax Reference
Note The lower integration limit is always zero (irrespective of the equilibrium angle). Also see: Copying Tables on page 158. If you wish to prevent this curve fitting.

Copy and Paste. this will facilitate generating a table of contents and also allows you to re-format the various styles (or import a custom set of styles using the style organiser in Word). fonts etc. Hence it is often most convenient to select the desired report page set up before any analyses have been made. their formatting will not be changed by changes to the print set up. Use the Format | Autoformat function in Word (with the default settings) to set the correct styles for the different levels of heading in the document. these should be saved and opened in a word processor such as Microsoft Word or Open Office for formatting:
set the results tables up as you want them to appear in the report (the report uses the same column widths. both Loadcase and Criteria results tables will not be split. printed. do the same for the graph widow. indentation and margin widths. once the tables have been placed into the report. This window is used to create a progressive summary of the analyses that have been carried out. Once all the results have been gathered in the report window. This report can be edited via Cut. However. as well as a ruler showing you tab stops.
Report Window
Hydromax contains a Report window. Underneath all of this you have your actual editing area. so choosing a wide paper size will prevent all but the widest tables from being split). However. Hydromax will split most results tables so they fit the specified page set up. You can for example choose the landscape Page Setup prior to running an analysis to make the tables fit better.Chapter 5 Hydromax Reference
Note When the graph is pasted in Microsoft Word®. the File | Page setup command allows you to customise the page orientation and size you wish to use for reporting. choose an appropriate paper size for the report (the tables will be split to fit this paper size. As the built-in report window only has basic editing and formatting functionality.
Report Window Page Setup
When you are in the Report window. the graph can be edited by right clicking on the graph and selecting “edit picture”.
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. copy and paste the Hydromax report into Microsoft word. inserted tables will be automatically formatted to fit the current page set up.
Editing a Report
The Report window has it's own toolbar permanently attached to the view. saved to and recalled from a disk file. it is recommended that the report window be used only to accumulate the results.). This is important because.

or the section of text that is currently highlighted. The format shown below is metric.the format you have displayed on your screen depends on the current Dimension Units you have (use Units in the Display menu to change this). in metric and in inches . The toolbar contains the following items: Font combo box Font Size combo box Bold Italic Underline Colour Left Justify Centre Justify Right Justify Bullet
Use this to change the current font Use this to change the current font size Use this to toggle the Bold style Use this to toggle the Italic style Use this to toggle the Underline style Use this to set Text Colour Use this to set Left Justification Use this to set Centre Justification Use this to set Right Justification Use this to toggle Bullet Points
The Ruler comes in two formats.
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. but it is strongly recommended not to use any of the formatting commands in the Report window.Chapter 5 Hydromax Reference
The information below is provided for reference. The toolbar has a number of buttons that allow you to change either the current settings.

The 'centre' tab stop centres the text at the current tab position. right. To clear a tab position. While the mouse button is depressed. The right tab stop is indicated on the ruler by an arrow with a tail toward the left. perform the analyses. The 'decimal' tab stop aligns the text at the decimal point. simply click the left mouse button on the tab symbol on the ruler. click the left mouse button at the specified location on the ruler. hold the shift key and click the right mouse button at the specified location on the ruler.Chapter 5 Hydromax Reference
The Ruler allows you to set left. To create a right tab stop. A paragraph can have as many as 20 tab positions. and decimal tab stops. The decimal tab stop is indicated on the ruler by a dot under a straight arrow. The centre tab stop is indicated on the ruler by a straight arrow. there are also several useful keystrokes that are available while editing the report.
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. This is useful if you wish to append an analysis to a report that had been calculated at some time in the past. click the right mouse button at the specified location on the ruler. The left tab stop is indicated on the ruler by an arrow with a tail toward the right. the tab command is then applicable to all the lines in the highlighted block of text. if you highlight a block of text before initiating a tab command. centre. the new results will be appended to the end of the report which may then be resaved). To move a tab position using the mouse. The 'left' tab stop indicates where the text following the tab character will start. To create a left tab stop. The tab stops are very useful for creating columns and tables. To create a decimal tab stop.
Keyboard Support for Reports
In addition to menu support. These are listed below for convenience: Ctrl+B Toggle Bold on/off Ctrl+U Toggle Underline on/off Ctrl+PageUp Ctrl+PageDown Ctrl+Enter Position at the top of the report Position at the bottom of the report Insert a page break
Opening and Saving the Report
The report can be saved to a file or read in from a file using the Save and Open Menu commands with the report window highlighted. The 'right' tab stop aligns the text at the current tab stop such that the text ends at the tab marker. drag the tab to the desired location and release the mouse button. a tab command is applicable to every line of the current paragraph. However. (Load in the old report. simply click on the desired tab marker and drag it off the ruler. hold the shift key and click the left mouse button at the specified location on the ruler. Normally. To create a centre tab stop.

Chapter 5 Hydromax Reference
Pasting images into the report
Sometimes. paste the image into Microsoft Word first. the image may not maintain its aspect ratio and may be pasted into the report as a square.
Toolbars
Hydromax has a number of icons arranged in toolbars to speed up access to some commonly used functions. The image copied is as per the image displayed in the Hydromax view window. To overcome this problem. then copy it from Word back into the Hydromax report window. Depending on which Microsoft operating system you are using (notably Win98). This is very easily done. it is desirable to insert schematic images of the vessel into the report.Delete Row | Sort Loadcase Rows – Move Loadcase/Tank Row up – Move Loadcase/Tank Row Down
View Toolbar
The View toolbar contains icons that execute the following commands: Zoom – Shrink – Pan – Home View – Rotate – Assembly window.
File Toolbar
The File toolbar contains icons that execute the following commands: New – Open – Save – Cut – Copy – Paste – Print
Edit Toolbar
The Edit toolbar contains icons that execute the following commands: Add Row . by copying an image from one of the design views and then pasting it into the report at the desired location.
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. You can hold your mouse over an icon to reveal a pop-up tip of what the icon does. Ensure that the colors selected will be easily visible in the white background of the report view.

Close
The Close command will delete the data in the frontmost window. the Open command will open whichever file corresponds to the frontmost input window. New creates a new compartment definition.
Open
When no design is open.
Save As
Selecting Save As performs the same function as save but allows you to specify a new filename preventing the original file from being overwritten. If a design is already open.
File Menu Edit Menu View Menu Case Menu Analysis Menu Display Menu Data Menu Window Menu Help Menu
File Menu
The File menu contains commands for opening and saving files and printing. Select the design you wish to open. The requested design will be read in and its hull shape calculated for use in Hydromax.
Menus
The following section describes all of the menu commands available in the Hydromax program. selecting the Open command will show a dialog box with a list of available Maxsurf designs. When the Compartment Definition table is frontmost.
Save
Selecting Save will save the contents of the frontmost window to a file on the disk.
Import
Allows import of file types other than Maxsurf design files
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.Chapter 5 Hydromax Reference
This toolbar provides a number of buttons for commonly used commands in case you should wish to customise your toolbars. Hydromax will ask whether you wish to save any changes. e.
New
Creates a new table for whichever input table is frontmost. click the Open button. the New command will create a new loading condition. Selecting Close when one of the design view windows is frontmost will close the current Maxsurf design.g: when the Loadcase Condition is the frontmost window.

The buoyant hull is exported as a single part with a single buoyant component (Non-buoyant volumes are included in this part as components with negative effectiveness). chose Edit | Activate GHS export. The following limitations currently apply.
Hydromax supports only a single buoyant hull part with one byouant component. so it is important to have unique compartment names). tanks and compartments and key points are all exported.
Hydromax v8. IGES exports the NURB surface data. compartment and non-buoyant volume is exported on a separate layer (the layer name being the same as the compartment name. bmp or png) file into the background of any of the Hydromax design views. but will be removed in subsequent versions:
Hydromax supports only a single buoyant hull part.0 file Also allows users to export Hydromax files that are compatible with earlier versions of Hydromax.
Export
Selecting Export enables you to export a Hydromax file as a variety of different file formats such as: DXF or IGES DXF exports sections as closed poly-lines. To enable the export command. A full GHS model file may be imported directly into Hydromax for analysis. It is possible that this might cause problems for some models where the section through the hull at a certain location contains more than one closed contour. tanks and sounding pipes are read from the GHS file. GHS If you have a Hydrolink license.Chapter 5 Hydromax Reference
nuShallo Allows direct import of a nuShallo pan file. In subsequent versions of Hydromax we will add the capability to divide the main buoyant hull into different components. The DXF file will be displayed in the design views. Linked negative tanks are not supported in Hydromax. Any container parts with elements with negative effectiveness will be read in as tanks. The full model including critical points. gif. three-dimensional model of the hull. Import Image Background Enables you to import an image file (jpg. In addition. The hull. Because the GHS file does not contain a full.
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. each tank. the geometry is locked: the tank geometry is locked and tanks cannot be added to the model. See the Maxsurf manual for more information. The buoyant hull part with the most sections is loaded from the GHS file. interconneceted. Sail parts are ignored
Import DXF Background Enables you to import a DXF file into Hydromax to use as construction lines. GHS Allows direct import of a GHS geometry file. you may export the Hydromax model to a GHS geometry file. All other cotainers are read in as tanks.

as this information is required for the export. After assigning the .
Allows you to export the rendered image as a bitmap file at the specified Import Main Criteria
Imports criteria from the selected criteria files. Fredyn Hydromax is able to export data suitable for input into Fredyn.xml file and also the location to which it should be saved. Current criteria may be kept or discarded. The groups are defined by selecting the surfaces to be measured and defining a boundary box that defines the limiting extents of the group.xml: Containing compartment definition . exporting Hydromax calibration results. all with the name you specify in the “Fredyn Export XML” dialog. and performed a tank calibration. The Export will generate 3 files.Chapter 5 Hydromax Reference
Export Bitmap Allows you to export the rendered image as a bitmap file at the specified resolution. To export use the File|Export|Fredyn… command. the following dialog will appear:
“Fredyn group definition” dialog
This dialog is where the user will specify the values for the variables used to generate the mesh file that defines the geometry of the hull. Fredyn mesh group definition When exporting from Hydromax to Fredyn you will be asked to name the . This command is only available when the Perspective window is frontmost with rendering turned on. hull form and compartment definitions into Fredyn input files. For more information on each of the fields in the table click on the Help button on the right hand side of the dialog. In the group definition dialog.out: Tank calibration results and compartment definitions . The most important part of the procedure is setting up the groups required in the mesh file.
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.txt: Mesh file representing the current hull shape.xml file name. any number of groups may be added and for each group. Contours will be formed through the selected surfaces and then trimmed back to the bounding box. Before doing the Fredyn export ensure you have specified the desired trim and heel ranges. The following files will be generated .

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Undo
Undo may be used with desk accessories. which have not been saved to disk. see Density of Fluids on page 150.
Save Densities As
Saves the Fluid densities table data. this is not normally necessary as this is done after any major changes to the criteria definition.
Rest Prob Damage Criteria to defaults
Results the probabilistic damage criteria to their default values.Chapter 5 Hydromax Reference
Save Main Criteria As
Exports the current criteria set to the specified file.
Cut
Cut may be used in the Report window but cannot be used on Hydromax drawing or data windows. including the design view.
Page Setup
The Page Setup dialog allows you to change page size and orientation for printing. Note that a branch of the criteria tree may be saved in its own file by right-clicking on the branch folder in the Criteria dialog tree.
Copy
The Copy command allows you to copy data from any of the windows.
Load Densities
Loads density table data previously saved from Hydromax – can be useful for synchronising the densities on several computers. but cannot be used on Hydromax drawing windows or data windows.
Edit Menu
The Edit menu contains commands for working with tables.
Exit
Exit will close Hydromax and all the data windows. results tables and graph window. It is good practice to save the criteria library with each project in a project folder.
Print
The Print command allows you to print the contents of the frontmost window on the screen. The whole library may be saved by right clicking on the root “Criteria” branch. Hydromax will ask you if you wish to save them before quitting.
Save Prob Damage Criteria As
As for main criteria but applies to the probabilistic damage criteria. If you have any data or results. input tables.
Import Prob Damage Criteria
As for main criteria but applies to the probabilistic damage criteria.

Paste cannot be used in the View. Merge Cells Merge the selected cells in a table into a single cell in the Report.
Add
The Add command is used to add an entry to the input tables (Load. otherwise all selected rows will be deleted.
Delete
The Delete command will delete rows from the input tables. Row Positioning Set Justification for the current table row or an entire table in the Report. Split Cell Split the currently selected cell into two separate cells in a table in the Report. margin line point etc. Insert Row Insert a new row into the current table in the Report. Graph or Results windows.
Select All
Selects the entire Report.
Table
Performs operations on Hydromax's Report window. Insert New Table Create a new table in the Report. If no rows are selected.Chapter 5 Hydromax Reference
Paste
Choose the Paste command to Paste data into the Loadcase window or other input tables. the last row in the window will be deleted.
Sort Items
Sorts the selected rows in the Loadcase window
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. Delete Cells Delete current cell. Cell Border Set Cell Border Width for a single cell or range of cells in the Report. or the Report window.
Fill Down
Copies text in a table down a column like a spreadsheet.). columns or rows in the Report. Cell Shading Set Cell Shading Percentage for a single cell or a range of cells in the Report. Show Grid Toggle table grid lines in the Report. tank. column or row or a range of cells.

Zoom
The Zoom function allows you to examine the contents of the design view windows in detail by enlarging the selected area to fill the screen. and Pan to arrange the view. Also see: Tolerances on page 146 Streaming results to Word on page 155.
Add Surface Areas
This command automatically adds the surface areas and centres of gravity of all hull surfaces into the current loading condition.
Rotate
Activates the Rotate command.
Home View
Choosing Home View will set the image back to its Home View size. It can also be used to release the Hydrolink license – a restart of Hydromax will be required for this to take effect. This is useful for estimating the initial weight of hull plating. To set the Home View.
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. then select Set Home View from the View menu.
Activate / Deactivate GHS Export
This command activates the GHS Import command in the File menu if a Hydrolink License is available. which is a virtual trackball which lets you freely rotate a design in the Perspective view window.
Shrink
Choosing Shrink will reduce the size of the displayed image in the design view windows by a factor of two. Shrink.
Set Home View
Choosing Set Home View allows you to set the Home View in the View window.Chapter 5 Hydromax Reference
Move Items Up
Moves the selected rows up (if possible) in the Loadcase and Compartment definition tables.
Preferences
The Hydromax preferences dialog allows you to set your analysis tolerances (or: error values) and select the option to stream the report to a Microsoft Word document.
Move Items Down
Moves the selected rows down (if possible) in the Loadcase and Compartment definition tables.
Pan
Choosing Pan allows you to move the image around within the View window. use Zoom.
View Menu
The View menu contains commands for controlling the views in the graphics windows.

Graph. When Loadcase window is frontmost. and graphs. which may be used to view parameters of selected objects (such as tanks). and Results windows. The item‟s current colour will be displayed on the left of the dialog. To change the colour click in the box and select a new colour from the palette. Curve of Areas. Remember to always be careful when using colour.
Font
Font command allows you to set the size and style of text. From the scrollable list. In general it is best to use a neutral background such as mid grey or dull blue and use lighter or darker shades of a colour rather than fully saturated hues. To Change the thickness select the thickness from the drop down list.
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. select the item whose colour you wish to change. Colours for the loadcase items can be set.Chapter 5 Hydromax Reference
Colours and lines
The Colours and lines function allows you to set the colour and thickness of the lines. See Loadcase Colour Formatting on page 44.
The text style chosen will affect the display and printing of all text in the Report.
Status Bar
Allows you to turn the Status Bar on and off at the bottom of the screen.
Assembly
Show or hide the assembly tree view.
Toolbar
Allows you to turn the Toolbars on and off. Loadcase.
Properties
Displays the properties sheet. It is very easy to get carried away with bright colours and end up with a garish display that is uncomfortable to work with. labels.

Case Menu
Commands associated with the Loadcases and Damage cases
Edit Loadcase
Edit the properties of the current Loadcase (name and whether it is a loadcase or Loadgroup). temporary damage conditionas are created automatically. See Working with Loadcases on page 38.Chapter 5 Hydromax Reference
Full Screen
Maximises screen usage.
Create cases from Zone Damage
Automatically creates damage cases based on the zones that have been defined for Probabilistic damage analysis.
Analysis Menu
The Analysis menu can be used to change the current analysis mode. (This is only required if you want to manually recreate some or all of the Proabilistic damage analysis conditions. the zone or sub-zone). number of Loadcases
Specify the number of loadcase tabs – this requires a restart to activate the changes made. It also contains commands to set the input data and analysis settings and environment options required for the current analysis.)
Max.
Add Damage case
Add another damage case
Delete Damage case
Delete the selected damage cases
Edit Damage case
Edit the properties of the selected damage case
Extent of Damage
Automatically finds the breached tanks and compartments due to a cuboid extent of damage (or in the case of Probabilisitic damage. Loadcases are created.
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. when running Probabilistic damage analysis. opened and closed through the file menu.

See Fluids Analysis Methods on page 148.
Trim
Allows the specification of the trimming mode to be used for the analysis. The vertical centre of gravity to be used for KN and Floodable Length analyses is specified here.Chapter 5 Hydromax Reference
Note: It is good practice when preparing to run analysis to work down the Analysis menu starting at the top and checking all of the settings and environment options. free-to-trim to loadcase. KN and Limiting KG analyses.
Specified Condition
Allows you to specify Heel. KG for the upright hydrostatics is also specified in this dialog.
Density
This command allows you to set the density of fluids used in the analysis. free-to-trim specifying initial trim value and free-totrim specifying LCG position.
Draft
The range of drafts used for the analysis of upright hydrostatics can be set using this command.
Calibration Options
Specify whether compartments and non-buoyant volumes should also be calibrated.
Displacement
The range of displacements used for the analysis of KN values. See Density on page 150.
Fluids
Allows you to specify whether to use Corrected VCG method or Simulate Fluid Movement method when treating the fluid contained in slack tanks. This can be fixed trim. Trim. Separate ranges are used for Large Angle Stability. Displacement and Draft for the Specified Condition analysis. Limiting KG and Floodable Length can be set using this command.
Heel
Selecting Heel allows you to specify the three ranges of heel angles that you wish Hydromax to step through.
MARPOL Options
Select MARPOL Regulation and specify which tanks should be incuded in the MARPOL oil outflow analysis.
Permeability
The range of permeabilities used for the Floodable Length analysis are set using this command. CG.
Waveform
The Waveform command allows you to perform analysis for a flat waterplane or sinusoidal or trochoidal waveforms.
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if you wish to recalculate at a different precision. ensuring that the margin line follows the hull shape precisely. It then updates the loadcase with the correct capacities and free surface moments for the tanks.
Update Loadcase
Checks for changed tanks and makes sure that any tanks and compartments that have not been formed are correctly calculated.
Snap Margin Line to Hull
Project all of the margin line points horizontally onto the hull surface.
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. tank and compartment sections and recalculates them from the hull surface data and compartment definition.Chapter 5 Hydromax Reference
Criteria
The criteria menu item will bring up the criteria dialog.
Grounding
Specifies grounding on one or two points of variable length for use with the Equilibrium and Longitudinal Strength analyses. Also recalculates totals and subsubtotals after a row sorting or moving command.
Recalculate Hull Sections
Deletes all existing hull. If any of the tank boundaries are made up from boundary surfaces. This is particularly useful if the underlying Maxsurf model has been modified. Also see: Margin Line Points on page 76. When the floodable length analysis is selected. Note: To be able to update the Hydromax model to changes made in Maxsurf see Updating the Hydromax Model on page 26 for a step-by-step procedure you can follow. This allows you to specify which criteria will be checked during the analysis. This command also updates the loadcase. See Criteria on page 163.
Set Analysis Type
Choose the analysis type you wish to use from the sub-menu. it is better to use “Recalculate Hull Sections” after re-opening the Maxsurf model to make sure the latest internal structure surfaces are being used as well. Also see: Tank Loads on page 46
Recalculate Tanks and Compartments
Forces all tanks and compartments to be re-formed from their initial definition. or if you wish to modify whether skin thickness or trimming options are applied. the criteria command will bring up a Floodable Length Criteria dialog with criteria that only apply to floodable length analysis.

which are displayed in the graphics and other windows. See Setting the Data Format on page 185.
Spool to Report
Send the results of the analysis to the report upon completion.
Stop Analysis
This command halts the analysis at the current iteration. A dialog box allows you to choose from a range of stability variables. equilibrium condition and KN values. Results are written to a tab delimited text file as specified by the user at the start of the analysis.
Hydrostatic results Data format dialog
Used to select display options for Criteria results:
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. any data displayed for the final iteration may be incorrect. also. Resume Analysis may be used to restart the calculation from the point where it was interrupted. This should be turned on before commencing the analysis to ensure that results are added to the report when the analysis is completed. Note that the analysis may not have been completed and in the case of large angle stability.
Data Format
Data Format allows you to choose which data are tabulated and graphed (Upright Hydrostatics. Equilibrium and Specified Condition). The analysis may be halted at any time by choosing Stop Analysis from this menu.
Resume Analysis
If you have halted analysis by choosing Stop Analysis.Chapter 5 Hydromax Reference
Start Analysis
Selecting Start Analysis causes Hydromax to start performing the specified analysis.
Start Batch Analysis
Hydromax will run the selected analyses for all combinations of load and damage cases using the batch processing command.
Display Menu
The Display menu contains commands for controlling the data. Stability.

Chapter 5 Hydromax Reference
Criteria table Data format dialog
Used to select which columns are displayed in the Loadcase window:
Loadcase Data format dialog
When the Max. Safe heeling angle angles graph is shown as a result of a Large Angle Stability analysis the Data Format dialog may be used to customise the graph layout:
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Large Angle Stability or Equilibrium analyses. hull contours.
Visibility
The visibility of tanks.Chapter 5 Hydromax Reference
Max safe heeling angle Data format dialog
May be used to customise the Floodable length graph:
Floodable length Data format dialog Set Vessel to DWL
Rotates the vessel back to upright and to DWL after an analysis has been completed (or Select View from Data used).
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. not for tanks with the vessel at the final heel and trim of the last analysis. and other items in the design view may be set by using this dialog. labels. The view may be set from any of the results from Upright Hydrostatics.
Select View from Data
This function may be used to synchronise the display in the Design View window with one of the sets of data in Results window. the Design View will change to match the condition in the selected row or column in the Results window. Simply highlight the column or row that corresponds to the condition you wish to view and select “Select View From Data”. compartments. the Loadcase will not update while editing – only when start another analysis).
Prob damage zones
Toggle the visibility of the probabilistic damage zones. This is required for automatic update of the Loadcase (note that if you do not rotate back to the DWL. This is to ensure that tank data in the Loadacase are for the vessel in the upright condition.

Also see: Show Single Hull Section on page 30
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Background
Controls whether the background DXF construction lines and the background images are displayed or not. Set Image Reference Point Sets the image reference point. This command is not available for images in the perspective window.. the section chosen can be changed by pressing the left or right cursor keys on your keyboard. a trimmed state at the end of an equilibrium analysis.
Design Grid
The grid submenu allows you to hide the grid or show the grid with or without station grid labels. The commands in the submenu are only available when a background image or DXF has been imported.
Show Single Hull Section in Body Plan
Selecting the Show Single Hull Section item from the Display menu will change the display in the Body Plan window to show only one section through the hull. Show Image Shows the image in the current view window. The option to display the grid will be greyed out when the ship is currently displayed in. Alternatively. The section being displayed can be chosen by clicking on the section indicators at the top of the control box. Tools for positioning and scaling the background image are also here. Switching analysis type puts the boat back into upright position on its design waterline. Delete DXF background Deletes the DXF background. similar to the one in Maxsurf. The background may be loaded from an existing DXF file using the Import function in the File menu. Set Image Zero Point Sets the image zero point.Chapter 5 Hydromax Reference
Individual Loadcase masses
Toggle the visibility of the individual mass items in the current loadcase. The grid can only be displayed when the vessel is in upright position on its design waterline. See the Maxsurf manual for more details Hide DXF Hides the DXF background. Show DXF Shows the DXF background. as well as a control box. in the top right corner of the window. for example. This allows you to rapidly step through the hull sections from bow to stern. Delete Image Deletes the background image in the current view window. Hide Image Hides the background image in the current view window.

giving a simple visual simulation of the motion of the hull through the wave. If animation is chosen after an Equilibrium Analysis has been performed in waves. You may set the initial viewing position in the Perspective View window using the Pitch. through the range of heel angles specified. When Hydromax has finished calculating the frames the sequence may be replayed by moving the mouse from side to side.
Design Grid
Access to the Design Grid is intended for information only. units for speed (used in wind heeling and heeling due to high-speed turn etc. Hold the shift key down while selecting the command to save the animation. The angular units for measuring heel and trim angles are always degrees. Render Transparent makes the hull surfaces of the model semi transparent so that the rendered tanks and compartments within the model may be viewed.
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. You are not expected to change the Design Grid in Hydromax. For example. when a waveform has been specified and an equilibrium analysis is selected or after a Large Angle Stability analysis over a heeling range.
Animate
This command is available for any analysis that steps through several steps. You are not expected to change the Frame of Reference in Hydromax. the animation will automatically cycle through the full range of wave phases. In addition to the length and mass units classes. criteria) and the angular units to be used for areas under GZ curves. may also be set.Chapter 5 Hydromax Reference
Render
When the Perspective window is the current view for the model the Render option may be toggled on and off to render the surfaces.
Render Transparent
When the Perspective window is the current view for the model the Render Transparent option may be toggled on and off. Roll and Yaw indicators. Selecting Animate will animate the stability sequence in the design View window. See Setting Units on page 37 for more information.
Frame of Reference
Access to the Frame of Reference is intended for information only.
Coefficients
Allows you to customise how you wish to calculate the coefficients as well as the display format for the LCB and LCF. See Customising Coefficients on page 36 for more information. Clicking the mouse button will terminate the animation.
Data Menu
Units
The units used may be specified using the Units command.

The Graph window displays a number of different graphs. Key Points.
Arrange Icons
Rearranges the icons of any iconised window so that they are collected together at the bottom of the Maxsurf program window.
Graph
Brings the selected Graph window to the front.
Tile Vertical
Layout all visible windows down the screen.
Cascade
Displays all the Windows behind the active Windows. The selected design window will then be brought to the front. These inputs are used to calculate the total Displacement and Centre of Gravity for Stability.
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Loadcase
Brings the Loadcase window to the front.
Help Menu
Provides access to Hydromax Help.
Hydromax Help
Invokes Hydromax Help. depending on which analysis mode is currently active. This will ensure that a consistent frame of reference is used in all the programs. See: Setting the Frame of Reference on page 18.
View Direction
Select the desired view direction from the sub-menu.
Window Menu
For the items in this menu.
Input
Choose from the Input item to bring the desired Input window to the front and display the Compartment Definition. Selecting the item brings the appropriate window to the front. The Loadcase window allows you to enter a series of component weights. each represents a Hydromax window.Chapter 5 Hydromax Reference
If the position(s) of the Baseline and/or Perpendiculars need to be changed from those defined in the Maxsurf model.
Results
Choose from the Results item to bring the desired Results window to the front and display the desired table. they may be changed using the Frame of Reference command. It is highly recommended that the correct frame of reference be set in Maxsurf prior to loading the design into Hydromax. together with their longitudinal and vertical distances from the zero point. KN and Equilibrium analysis. Margin Line Points or Modulus table.
Tile Horizontal
Layout all visible windows across the screen.

Chapter 5 Hydromax Reference
Hydromax Automation Reference
Invokes the Automation Reference help system.
Online Support
Provides access to a wide range of support resources available on the internet.
Check for Updates
Provides access to our website with the most recent version listed.
About Hydromax
Displays information about the current version of Hydromax you are using.
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) is achieved in Hydromax.
Definition and calculation of form parameters
Below is a summary of the definitions of basic vessel particulars and form parameters used in Hydromax. static waterline and “vertical” measurements are perpendicular to the waterline
Rotated reference frame (red) and measurements in the two reference frames: Measurements in the upright vessel reference frame (green) and trimmed reference frame (blue)
When the vessel is upright (zero trim and zero heel) these axis systems are parallel. “Longitudinal” measurements are made parallel to the baseline and “vertical” measurements are perpendicular to the baseline. because Hydromax treats trim exactly (the hull is rotated not sheared when trim occurs).
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. these axis systems are no longer parallel. World or trimmed frame of reference The “world” or “trimmed” reference frame is that of the trimmed vessel. “Longitudinal” measurements are made parallel to the horizontal. and investigates why differences with other hydrostatics packages may occur. However.Appendix A
Appendix A: Calculation of Form Parameters
This Appendix explains how the calculation of form parameters (CB.
Measurement Reference Frames
Results in Hydromax are given from the vessel‟s zero point. CP. However if the vessel is trimmed or heeled or rotated in both directions simultaneously. etc. Here the baseline is horizontal and the perpendiculars are vertical. Here the baseline is no longer horizontal and neither are the perpendiculars vertical. AM. there are two frames of reference: Ship or upright frame of reference The “ship” or “upright” reference frame is that of the upright vessel with zero-trim.

It is for this reason that. and measurements from the keel such as KB and KG. then there will be a sin(trim angle) term introduced. KM is not equal to KB+BM (BM is in a different axis system to KB and KM. LCF. Similarly. floatation and buoyancy (LCG. are measured in the “world” frame of reference. LCG is not equal to LCB – if both LCB and LCG are measured in the ship-axis system (of course if they are measured in the earthfixed axis system then they are the same.Appendix A
Ship-Fixed and Earth-Fixed(world) axis systems
The majority of measurements are given in the “ship” frame of reference.
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. The same is true of TCB and TCG if the vessel is heeled. GM is the true vertical separation of the metacentre and the centre of gravity with the vessel inclined and are always measured normal to the water surface. Thus the metacentre is always vertically (in the earth-fixed axis system) above the centre of buoyancy by a distance BM = I / vol where I is the second moment of area of the waterplane. GM. These include longitudinal centres of gravity. i. in general. Measurements such as BM. LCB). that are explicitly vertical. in generally for the vessel to be in equilibrium. This is because if the vessel is trimmed and if the VCG and VCB are not the same. and only if the vessel is upright are the axis systems parallel and hence the equation holds).e.

measured in the trimmed reference frame Distance from keel (baseline) to centre of buoyancy. measured in upright reference frame. Longitudinal Centre of Floatation. Length overall Longitudinal Centre of Buoyancy. measured in upright reference frame. measured normal to the baseline. parallel to baseline. Distance from keel (baseline) to centre of gravity. These can be modified in the Data | Coefficients dialog shown below:
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. Length of design waterline Length between perpendiculars length of waterline under investigation Draft from some arbitrary baseline (normally the lowest point on the design) Maximum immersed depth (draft) of hull Draft (immersed depth) of station under investigation Immersed volume of displacement at waterline under investigation
Coefficient parameters
There are several options for calculating hullform coefficients.Appendix A Nomenclature
Amax Ams A AWP BOA BWL B b GM
KB KG LOA LCB LCF LCG LWL LBP L T0 T t
Maximum immersed cross-sectional area to waterline under investigation Immersed cross-sectional area to waterline under investigation amidships Immersed cross-section area: Amax or Ams as selected by user Area of waterplane at the waterline under investigation Overall beam of whole vessel (above and below waterline) Maximum waterline beam at design waterline Maximum beam of waterline under investigation Waterline beam of station under investigation Metacentric height: vertical distance from centre of gravity to metacentre. measured normal to the baseline. measured in upright reference frame. parallel to baseline. parallel to baseline. Longitudinal Centre of Gravity.

this may be different from the length of the DWL (LWL) and in general. it may be more appropriate to define an effective length of the underwater body. In addition. Prismatic and Waterplane Area Coefficients. In some cases. particularly for resistance prediction purposes. it may be appropriate to use the actual waterline length at that draft (L). The forward perpendicular is normally defined as the intersection of the DWL with the bow. features such as bulbous bows and overhangs can make the LBP. LWL and LOA quite different. for calculations at drafts other than the DWL. or possibly the transom. will also be different from the LOA (overall length). Select Coefficients from the Display menu:
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.
In Hydromax you may choose between the length between perpendiculars and the waterline length for the calculation of Block.Appendix A
Length
The datum/design waterline or DWL is a waterline near which the fully loaded design is intended to float under normal circumstances.
Some of the more common lengths that may be used to characterise a vessel. Several lengths may be defined: the LBP is the length between perpendiculars. The after perpendicular is normally defined as the position of the rudder post.

g. In some cases the overall beam is of importance.
Multihull beams
You may choose which beam should be used from the following list:
In the reported hydrostatics. the beam used would be the sum of B1. and this may be of the DWL or the waterline under consideration. you can select various beams:
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. However. For the case of a monohull this will be the normal waterline beam. vessel with tumble-home or blisters).
Vessel with tumble-home
Catamarans and other multihull vessels pose another difficulty. Hydromax uses the total waterline beam of immersed portions of the section for calculation of block coefficient and other form parameters. submarine. For the section shown below. For catamarans this will be twice the demihull beam (remember that the total displaced volume is used and hence the block coefficient is the same as that of a single demihull). there may be times when it is appropriate to use the maximum immersed beam (e. in others. the beam of the individual hulls may be required.Appendix A
Beam
It is normal to use the maximum waterline beam for calculation of coefficients. B2 and B3. For the calculation of section area coefficients it is normal practice to use the beam and draft of the section in question.

include the appendages. Normally this datum is the lowest part of the upright hull. For a monhull.:
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. It should be noted that the section area will.
Draft
The draft is normally specified from a nominal datum. Hydromax uses the depths that stations extend below the waterline for calculation of form coefficients. Both depths are measured in upright position. this will be the same as the extents value. however. this would simply be the distance from the port side to the starboard side. but for a multihull. For a monhull without tunnels. the datum may be elsewhere. However. The other beam values are calculated by summing the breadth of waterline crossings as described above. this is often the case when form parameters are calculated. For a catamaran this would be from the outside of the port demihull to the outside of the starboard demihull. for vessels with raked keel lines or yachts. However. there are also occasions when the immersed depth of the section is a more relevant measure of draft.Appendix A
Calculated beams
The values “Beam extents” are those that measure the beam across the maximum port and starboard extents of the vessel. it will be less than the extents value. Hydromax uses these values for computing coefficients. including the option of measuring the draft to the baseline – this gives the option of ignoring appendages such as fin keels when determining the draft to be used to calculate the form parameter (if the baseline is defined to the bottom of the canoe body for example). You may select which depth should be used for the calculation of form parameters. In Hydromax drafts are defined from the datum line.

Essentially the draft is measured along the heeled and trimmed perpendiculars on the centreline. It is for this reason that as the heel approaches 90degrees.
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. the draft is measured through the intersection of the upright waterline and the centreline. For vessels with no parallel mid-body.
Difference between “Immersed depth” and “Draft” measurements
Midship and Max Area Sections
It is current usual practice to define the midship section as midway between the perpendiculars. however for some vessels it is defined as the midpoint of the DWL. the draft becomes very large. In Hydromax.
Draft measured along the inclined perpendicular lines
Immersed depth and Draft measurements The images below show the difference between the draft measurements (which are made in the inclined centreline plane of the vessel) and the immersed depth measurements (which are made normal to the free-surface). the position midway between the perpendiculars is defined as midships. the section with greatest cross-sectional area may also be of particular interest. perpendicular to the heeled waterline (see figure below).Appendix A
Draft measurements
Draft measurement at heel angle When the vessel is heeled.

the actual definitions of the length." However.
Block Coefficient
Principles of Naval Architecture defines the block coefficient as: "the ratio of the volume of displacement of the moulded form up to any waterline to the volume of a rectangular prism with length. Length may be LBP. is calculated at either the station with maximum cross-sectional area or the midship section area (as defined in the Coefficients dialog). the midship section coefficient can be greater than unity. The beam used is that obtained by summing the immersed waterline crossings of the specified section. The section area coefficient used by Hydromax.Appendix A
When computing form coefficients. LWL or some effective length. such as CP and CM. The beam and immersed depth of the selected section is used unless the draft to baseline option has been selected in which case this draft is used. beam and draft used vary between authorities. for sections that have significant tumble-home or blisters below the waterline. In Hydromax midships is midway between the perpendiculars. Hydromax uses the length beam and draft as selected in the Coefficients dialog to compute the block coefficient. or may be defined according to another standard – this may be important for hulls with significant tumble-home or blisters below the waterline.
CB
L B T
Section Area Coefficient
Principles of Naval Architecture defines the midship coefficient as: "The ratio of the immersed area of the midship station to that of a rectangle of breadth equal to moulded breadth and depth equal to moulded draft at amidships.
Options for Section area coefficient
CM
A b t
Prismatic Coefficient
Principles of Naval Architecture defines the prismatic coefficient as:
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. you may select which section area should be used: Hydromax uses the station with the maximum immersed cross-sectional area at the waterline under consideration. The beam may be at amidships or the maximum moulded beam of the waterline. breadth and depth equal to the length." It should be noted that. breadth and mean draft of the ship at that waterline.

When the vessel is free-to-trim. See Customising Coefficients on page 36 for more information. This is explained in the figure below:
Effect of vertical separation of CG and CB on LCG and LCB measured in the Ship reference frame
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.Appendix A
"The ratio between the volume of displacement and a prism whose length equals the length of the ship and whose cross-section equals the midship section area." Again the definition of midship section and vessel length depend on the standard being used. see Measurement Reference Frames on page 214. Hydromax uses the selected length and the selected immersed cross-section area Amax or Ams." Hydromax uses the length and beam as selected.
CWP
AWP L B
LCG and LCB
Hydromax allows you to fully customise how you want to display the LCB and LCF values. the LCG and LCB will be at the same longitudinal position in the global coordinate system. Therefore a difference between the LCG and the LCB value will occur when the vessel is trimmed. but not in the frame of reference. The LCG and LCB are calculated in the “ship” or “upright” frame of reference.
CP
L A
Waterplane Area Coefficient
Principles of Naval Architecture defines the waterplane area coefficient as: "The ratio between the area of the waterplane and the area of a circumscribing rectangle.

Hydromax calculates the steepest slope of the deck when the ship is trimmed and/or heeled.
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. Deck camber and initial deck slope are not taken into account. The unitlength can be either in cm or inch depending on your unit settings. This is the same for differences in TCG and TCB values due to heeling.
Maximum deck inclination
The inclination angle is a combination of heel and trim angle.
MTc or MTi
The required moment to make the vessel trim one unit-length.
Trim angle
The trim angle as defined by:
tan
1
Ta
Tf L pp
where: is the trim angle.
Immersion
The weight required to sink the model one unit-length below its current waterline.Appendix A
Note: LCG and LCB are calculated in the vessels‟ frame of reference and therefore will have different longitudinal positions when the vessel is trimmed then for when it is upright. That can be either cm or inch depending on your unit settings. Tf are the aft and forward drafts at the corresponding perpendiculars and LPP is the length between perpendiculars. assuming the deck inclination is zero when the vessel is in upright position. For example:
The Max deck inclination is the maximum slope of the deck when combining the trim and heel angle of the vessel. Ta .

agreement of hand calculations to within 2% is considered good). and most automatic calculations carried out by computers. As with all numerical integration schemes. Differences in derived form parameters may show considerable variation. due to the increased speed and accuracy with which these calculations may be carried out. It may be shown that the area obtained by integrating the girth of the sphere along its length is given by:
R2 . The 0. are under 0.Appendix A RM at 1 deg
The righting Moment at 1 degree heel angle. These effects are noted from comparing the results of different hydrostatics packages on the same hullform. and number of interpolation points used to define each section. differences for basic parameters such as displacement etc. If the surface is exported as DXF poly-lines then the precision used and the number of straight-line sections used to make up the poly-line are important. or higher order methods. The differences are easily shown by considering the surface area of half a sphere. in a similar way that one might integrate the station cross-sectional area along the length of the hull to obtain the volume. and occur in both hand calculations. The integration method used: trapezium. These mainly occur from the integration method used. Both methods use numerical integration techniques.5 2 R 2 A'
approximately 27%. the accuracy increases as the step size is reduced. and the wetted surface area can only be accurately found by summing elemental areas over the complete surface. this is primarily due to differences in the definitions used – see discussion above. which are normally either based on Simpson's rule or the Trapezium rule. where R is the radius of the circle. in general. The only accurate numerical method is to sum the areas of individual triangles interpolated on the parametric surface. and hence the 2 2 R2 integration of section girths underestimates by error factor of 4/ 1. Differences in the hull definition. note that this is with an infinite number of integration steps. In general. may be attributed to a number of causes:
Convergence limits when balancing a hull to a specified displacement or centre of gravity. With hand calculations. However. This can be of particular importance if the waterline intersects the stem profile between two sections.
Integration of wetted surface area
At first glance.5% error discrepancy noted above.5% (note that. this is not the case. or 0. the stations should be more closely spaced. This is given analytically by: A 2 R 2 .27 . However. with computer calculations. it is quite feasible to use 200 sections or more with 10s of significant figures. hence computer calculations offer an enormous advantage compared with hand calculations. it is normal to use perhaps 21 sections and perhaps 3-5 significant figures. such as near the bow and stern. Where there are large changes in shape. calculated by
RM
Displ *GMt * sin(1)
Potential for errors in hydrostatic calculations
There are a number of potential sources of error when calculating the hydrostatic properties of immersed shapes. it may seem that wetted surface area may be calculated by simply integrating the station girth along the length of the hull. and their distribution. Simpson. the error due to integrating girths along the vessel length cannot be removed simply by increasing the number of integration stations.
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2
. Different number of integration stations used. Further.

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. since they are derived from the actual parametric definition of the surface. Those calculated by Hydromax and most other hydrodynamics packages. due to the greatly reduced longitudinal curvature. Surface areas calculated by the 'Calculate Areas' dialog in Maxsurf are the most accurate. for normal ship hulls the differences will be much less. which use a number of vertical stations to define the hull.Appendix A
However. will be subject to the error described above.

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. The first section of the file is the units section and this specifies the units that are to be used in the file. The criteria then appear after the units section and as many criteria as required may be included. it is not possible to edit the criterion‟s parameters in Hydromax The other parameters that may be set depend on the criterion type.rtf true STIX input data true false false GreaterThan 0. The common parameters for all criteria are as follows: Type Describes the type of criterion RuleName Text which specifies the rule to which the criterion belongs CritName Text which specifies the criterion‟s name CritInfo Verbose description of the criterion Locked Whether the criterion may be edited in Hydromax or not.g. There are two angular units: AngleUnits Specifies the units for angular measurements. range of stability GZAreaGMAngleUnits Specifies the angle units used for area under GZ graph and for GM.Appendix B
[criterion] Type RuleName CritName CritInfo CritInfoFile Locked GroupName TestIntact TestDamage Test Compare RequiredValue [end]
= = = = = = = = = = = =
CTStdAngleOfVanishingStab STIX input data Angle of vanishing stability Calculates the angle of vanishing stability… HMCriteriaHelp\StixHelp. If Locked is set to true.0
The file must have “Hydromax Criteria File” in the first row. e.

If there are any other calculations that you would like implemented. and the IMO required GM for vessels carrying grain in bulk. This allows for complex calculations to be cross referenced into criteria.
Selecting a calculation in a criterion
Using a calculation in a criterion is very similar to using a heel arm:
Define your custom calculation by copying it from the parent list. Currently this has only been implemented for the IMO roll-back angle calculation used in the IMO code on Intact Stability. you should make a copy of the parent calculation by dragging it to your custom criteria folder.Appendix F
Appendix C: Criteria Help
In this Appendix all individual Parent Criteria are explained in detail.
Parent Calculations
Special calculations are provided for some criteria parameters. The parent calculations are listed above the parent heeling arms:
Parent calculations in Hydromax Criteria dialog
As with other criteria and heeling arms. In the criterion select the required calculation from the pull down list:
Angle calculators
These calculators produce an angular measurement and may be referenced by the following criteria:
Criteria that currently support roll-back angle calculations
Heeling arm criteria (xRef) Combined
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Ratio of areas type 2 Combined criteria (ratio of areas
XRefHeelRatioOfAreas2 XRefHeelGenericWindHeeling
. severe wind and rolling (weather) criterion. see Chapter 4 Stability Criteria on page 163. This information can also be found in the lower right of the Criteria Dialog in the Criteria Help section. please contact support@formsys.com with details of the required calculations. In this section:
Parent Calculations Minimum GM Calculators Parent Heeling Arms Parent Heeling Moments Parent Stability Criteria
For all general help on criteria or working with the criteria dialog.

as defined in IMO Resolution MSC.25 B
0.general wind heeling arm Combined criteria (ratio of areas type 2) . combined criteria (stand alone)
type 2) Ratio of areas type 2 . The block coefficient is calculated with the current user settings for length and beam (not necessarily the waterline beam which another parameter required for the calculation).23(59).7” or “Tabulated value for k” – these are auto completed so you only need to type the first letter.Appendix B
heeling arm criteria (xRef) Heeling arm criteria (stand alone) Heeling arm. “Sharp bilge: k = 0.wind heeling arm
CritHeelWindHeeling
IMO roll-back angle calculator
The IMO roll back angle calculator calculates the roll back angle as per the severe wind and rolling (weather) criterion as defined in the IMO Code on Intact Stability.749(18) and MSC.general wind heeling arm CritHeelRatioOfAreas2
CritHeelGenericWindHeeling
Combined criteria (ratio of areas type 2) .0875 SF
Where (using consistent units): L is the combined length of all full compartments
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. The method used for the k-factor can be one of three options: “Round bilge: k = 1.0”. This calculation follows the function defined in the Intact Stability codes A.
Input parameters for: IMO roll-back angle calculation
GM calculators
These calculators produce a GM measurement and may be referenced by the following criteria:
Criteria that currently support roll-back angle calculations
GZ curve criteria
Value of GMt at (calc)
CTStdValueOfGMAt
Minimum GM calculator – Grain
The required GM for vessels carrying grain. combined criteria (stand alone) Heeling arm. The input parameters may be specified by the user or calculated by Hydromax for the vessel in the upright condition for the current loadcase.645 B Vd
0.267(85). is calculated as follows:
GM
L B Vd 0.

170. k0 and k1 are constants.0025 Ton/ft2 and k1 = 14200 ft4/Ton k0 = 0.0033 Ton/ft2 and k1 = 14200 ft4/Ton k0 = 0.055 t/m2 and k1 = 1309 m4/t For CFR 46. H is the height of the assumed centre of lateral resistance of the vessel. h is height of the centroid of A above the zero point. Δ is the vessel displacement 0 is a critical heel angle which may be a fixed angle or a fraction of the deck-edge or marginline immersion angle A is the windage area which may be specified as a total area or as an area additional to the area of the hull above the waterline.005 Ton/ft2 and k1 = 14200 ft4/Ton k0 = 0. for example: For CFR 46. required GM Minimum GM calculator – Wind pressure
The GM required to withstand wind pressure is calculated as follows:
k0 GM
L k1
2
A(h H ) cos n ( 0 ) sin( 0 )
Where (using consistent units): L is the waterline length of the vessel (if the criterion required LPP or LOA then enter the value directly rather than having it calculated by Hydromax.036 t/m2 and k1 = 1309 m4/t For CFR 46. 170.170: ocean service: k0 = 0.170: service on protected water: k0 = 0.Appendix F
B is the moulded breadth of the vessel SF is the stowage factor Vd is the calculated average void depth Δ is the vessel displacement
Input parameters for: Grain heeling min.028 t/m2 and k1 = 1309 m4/t
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. 170.170: service on partially protected water: k0 = 0.

171.0 K
Where N is the number of passengers. An example of where this calculation should be used is in CFR 46.
Input parameters for: Constant min.Appendix B
Input parameters for: Wind pressure min.050:
GM
Nb with a K tan( 0 )
Nb and m. n = 1. n are the exponents for sine and cosine. required GM Minimum GM calculator – Constant with freeboard
The required GM is calculated as follows:
GM
a f
B fa
cos n ( 0 ) sin m ( 0 )
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Where (using consistent units):
. required GM Minimum GM calculator – Constant
The required GM is calculated as follows:
GM
a cos n ( 0 ) sin m ( 0 )
Where (using consistent units): a is a constant arm or moment (depending on whether the vessel displacement is used) 0 is a critical heel angle which may be a fixed angle or a fraction of the deck-edge or marginline immersion angle m. b is their average transverse location and K is the number of passengers per unit mass.

fa is the additional freeboard allowance calculated as follows (additionally the freeboard allowance may be limited to a maximum specified value):
fa
k h
l L
2b b0 B
b1
Where (using consistent units): L is the waterline length of the vessel (if the criterion required LPP or LOA then enter the value directly rather than having it calculated by Hydromax. typically the length of the watertight trunk b is a breadth.
Heeling Arm Definition
This section describes how to define heeling arms and is valid for both the parent heeling arms that can be cross referenced into the heeling arm criteria.
Parent Heeling Arms
As with the criteria.
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. there is a list of parent heeling arms. from which custom heeling arms may be derived:
Available heeling arms and moments
To learn how to cross reference these heeling arms into criteria. B is the same as that used in the expression for GM k is a dimensionless constant h is a height. and for the Old heeling arm criteria where the heeling arm is specified for each criterion separately.Appendix F
a is a constant arm or moment (depending on whether the vessel displacement is used) B is the vessel beam f is the minimum freeboard for the upright (zero heel) condition to the deck-edge or marginline. typically the breadth of the watertight trunk b0 is a constant with the same units as b b1 is a dimensionless constant If desired. n are the exponents for sine and cosine. a heel adjustment may be included: 0 is a critical heel angle which may be a fixed angle or a fraction of the deck-edge or marginline immersion angle m. typically the height of the watertight trunk l is a length. please see Heeling arm criteria (xRef) on page 260.

cosn describes the shape of the curve.
Typically n=1 is used for passenger crowding and vessel turning since the horizontal lever for the passenger transverse location reduces with the cosine of the heel angle. such as IMO Severe wind and rolling (weather criterion) have a heeling arm of constant magnitude. in this case n=0 should be used. For wind n=2 is often used for heeling because both the projected area as well as the lever decrease with the cosine of the heel angle.
H steady ( ) H gust ( )
A cosn ( ) A GustRatio cosn ( )
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. Same as for the Parent criteria.
General heeling arm
The general form of the heeling arm is given below:
H( )
where:
A cos n ( )
is the heel angle.
GustRatio
H gust H steady
Both the steady and the gust heel arm have the same shape.
General heeling arm with gust
Some criteria require a Gust Ratio.Appendix B
There are several heeling arms that are used for the criteria. this is the ratio of the magnitude of the wind heeling arm during a gust to the magnitude of the wind heeling arm under steady wind. the Parent heeling arms will be reset to their default values each time you start up Hydromax. However. Make sure you read Important note: heeling arm criteria dependent on displacement on page 240.
General heeling arm General heeling arm with gust General cos+sin heeling arm User Defined Heeling Arm Passenger crowding heeling arm Wind Turning Lifting heeling Towing heeling Forces heeling arm Trawling heeling arm Grain heeling arm Areas and leavers Important note: heeling arm criteria dependent on displacement
Note: When you are working with the parent heeling arms. make sure you copy them into a custom heeling arms folder before editing them. They are defined below. some criteria.
A is the magnitude of the heeling arm.

the definition of gust ratio is the ratio of the heeling arms. and if a value preceded by a comma is given.) A single coefficient may be adjusted and this is used as a multiplication factor (whist the shape of the curve remains unchanged).2 meters at 45 degrees angle of heel. This heeling arm can then be cross-referenced into any of the heeling arm criteria. the same heeling arm form may be used for computing towing heeling arms of the form:
H( )
k A cos(
) B sin(
)
in this case a constant angle (in the case of towing. It may be shown that this is equivalent to:
H( )
where:
k C cos( ) D sin( )
R2 1 tan 2 (
C
) . First. the user can specify the number of points and the shape of the heeling arm curve. These should be comma delimited for example <45 .Appendix F
where: is the heel angle.2> for a heeling arm magnitude of 1.
General cos+sin heeling arm
Some criteria. the angle of the tow above the horizontal) is included. the number of points is specified and then for each point the angle and magnitude of the curve can be specified. if only one value is supplied it is taken as the heel angle – and the magnitude is left unchanged.
It should be noted. R2
A2
B 2 and
tan
B A
Make sure you read Important note: heeling arm criteria dependent on displacement on page 240. Some criteria specify the ratio of the wind speeds. notably lifting of weights.
cosn describes the shape of the curve. With the heeling arm. require a heeling arm with both a sine and cosine component:
H( )
k A cos n ( )
B sin m ( )
It should be noted that provided the indices are both unity. (To aid input of the data.
User Defined Heeling Arm
A user-defined heeling arm may be used in the criteria. the ratio of the heel arms will be the square of the ratio of the wind speeds. 1.
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. that in this case. A is the magnitude of the heeling arm. this is taken as the magnitude – and the heel angle is left unchanged. if it is assumed that the wind pressure is proportional to the square of the wind seed. D
C tan(
) .

defines shape
mass length none
In the case of the wind pressure based formulation. the wind heeling arm is given by:
Hw( )
a
PA h H cosn ( ) g
where: a is a constant.Appendix B
Passenger crowding heeling arm
The magnitude of the heel arm is given by:
H pc ( )
where:
n pas MD
cosn ( )
n pas is the number of passengers M is the average mass of a single passenger D is the average distance of passengers from the vessel centreline is the vessel mass (same units as M )
The heeling arm parameters are specified as follows: Option number of passengers: nPass passenger mass: M distance from centreline: D cosine power: n
Wind heeling arm
Description Number of passengers
Units none
Average mass of one passenger Average distance of the passengers from the centreline Cosine power for curve . the wind heeling arm is given by:
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. theoretically unity A is the windage area at height h is the vessel mass P is the wind pressure H is the vertical centre of hydrodynamic resistance to the wind force In the case of the wind velocity based formulation.

Appendix F
Hw( )
a
v2 A h H cosn ( ) g
where: a is now effectively an average drag coefficient for the windage area multiplied by the air density and has units of density v is the wind speed.defines shape
length
length length
length none
The magnitude of the heel arm is derived from the moment created by the centripetal force acting on the vessel during a high-speed turn and the vertical separation of the centres of gravity and hydrodynamic lateral resistance to the turn. mass/length3 for velocity based formulation
wind model wind pressure or velocity
area centroid height: h total area: A additional area: A
height of lateral resistance: H
H = mean draft / 2 H = vert. H is taken as the vertical centre of underwater lateral projected area.depends on wind model mass/(time2 length) or length/ time length length2 length2 Units none for pressure based formulation.5 ρair CD for the velocity formulation. normally unity for pressure based formulation or 0. theoretically unity v is the vessel velocity
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. centre of projected lat. The heeling arm is thus given by:
Ht ( )
v2 a h cos n ( ) Rg
where (in consistent units): a is a constant. u'water area H = waterline cosine power: n
Turning heeling arm
Height of user defined total or additional windage area User may specify either a total windage area Or. The heeling arm is obtained by dividing the heeling moment by the vessel weight. where ρair is the density of air and CD is an average drag coefficient for the windage area Pressure or Velocity (type “P” or “V”) Actual velocity of pressure . Option constant: a Description Constant which may be used to modify the magnitude of the heel arm. H is taken as the waterline Cosine power for curve . And the other parameters are described as above. an area to be added to the windage area computed by Hydromax based on the hull sections There are four options for specifying H (all options are calculated with the vessel upright at the loadcase displacement and LCG): User specified H is taken as half the mean draft.

) The magnitude of the heel arm is given by:
H lw ( )
M
h cos( ) v sin( )
where: M is the mass of the weight being lifted h is horizontal separation of the centre of gravity of the weight in its stowage position and the suspension position (upper tip of lifting boom) v is vertical separation of the centre of gravity of the weight in its stowage position and the suspension position (upper tip of lifting boom) is the vessel mass (same units as M )
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. as percentage of LWL There are four options for specifying h (all options are calculated with the vessel upright at the loadcase displacement and LCG): User specified h is taken as KG . R.position of G above baseline in upright condition h is taken as KG less half the mean draft. as some criteria require.mean draft / 2 h = KG . the vessel displacement remains constant. i.Appendix B
R is the radius of the turn h is the vertical separation of the centres of gravity and lateral resistance
The heeling arm parameters are specified as follows: Option constant: a vessel speed: v turn radius: R turn radius. centre of projected lat.defines shape Units none length/time length % length
h = KG h = KG .e. Cosine power for curve . as percentage of LWL Vertical lever: h Description Constant which may be used to modify the magnitude of the heel arm. h is taken as the vertical separation of the centres of gravity and underwater lateral projected area. but there is an effective change of its centre of gravity. u'water area cosine power: n
Lifting heeling arm
length length length
none
This is used to simulate the effect of lifting a weight from its stowage position.vert. (The weight is lifted from a stowage position onboard the vessel by a crane on the vessel. normally unity Vessel speed in turn Turn radius may be specified directly Or.

expressed as a force. This value is positive if the suspension position (upper tip of lifting boom) is above the original stowage position. Units mass length
horizontal separation of suspension from stowage position: h
length
Towing heeling arm
The magnitude of the heel arm is given by:
H tow ( )
T v cosn ( g
) h sin(
)
where: T is the tension in the towline or vessel thrust. Angle of tow above the horizontal Cosine power for curve . Horizontal offset of the tow attachment position from the vessel centreline. h is horizontal offset of the tow attachment position from the vessel centreline v is vertical separation tow attachment position from the vessel‟s vertical centre of thrust is the vessel mass is the power index for the cosine term which may be used to change the shape of the heeling n arm curve is the (constant) angle of the towline above the horizontal. Horizontal separation of suspension point (upper tip of lifting boom) from weight‟s original stowage position on the vessel This value is positive if the horizontal shift of the weight should produce a positive heeling moment. It is assumed that the towline is sufficiently long that this angle remains constant and does not vary as the vessel is heeled. This value is positive if the offset is in the direction of the tow. The heeling arm parameters are specified as follows: Option tension or thrust: T vertical separation of propeller centre and tow attachment: v horizontal offset of tow attachment: h Description Tension in towline or vessel thrust Vertical separation tow attachment position from the vessel‟s vertical centre of thrust.Appendix F
Just before lifting the weight off the vessel’s deck
The heeling arm parameters are specified as follows: Option Mass being lifted: M vertical separation of suspension from stowage position: v Description Mass of weight being lifted Vertical separation of suspension point from weight‟s original stowage position on the vessel. such as those applied due fire-fighting or manoeuvring using thrusters.defines shape Units force length
length
angle of tow above horizontal: tau cosine power: n
Forces heeling arm
angle none
This heeling arm can be used to model up to two forces acting on the vessel forces. The magnitude of the heel arm is given by:
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. This value is positive if the towline is above the thrust centre.

expressed as a force.
n1 and n2 define the shapes of the heeling arms created by the two forces. λ0) Point B = ( 1 deg heel.
The equation of the
H grain ( )
0
1 abs
(1
1
)
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. α λ0) i. is the vessel mass
Grain heeling arm
This heeling arm can be used model the effects of bulk grain shift as defined in IMO Resolution MSC. H is the assumed vertical position of the vessel‟s centre of lateral resistance (or the centre of
rotation from which the forces are applied) is the vessel mass g is acceleration due to gravity
Trawling heeling arm
This heeling arm can be used model the effects of trawl net snagging as defined in Annex G of the Australian NSCV requirements:
H trawling ( )
m y cosn ( ) m
where: m is a mass parameter determined from the breaking load of the trawl gear and the downwards angle of the trawl net. not a mass. h1 and h2 are the vertical heights (from the zero point) at which these forces act.23(59): The heeling arm is defined by a straight line through two points A.Appendix B
H forces ( )
1 A1 h1 g
H cosn1 ( )
A2 h 2
H cosn2 ( )
where: A1 and A2 are two forces acting on the vessel.e the heeling arm magnitude is reduced by a factor α at a heel angle of line is given below:
1. B. y is the transverse distance of the line of action of the trawl wire from the vessel centreline n defines the shape of the heeling arm. Point A = (0 deg heel. It is mirrored about the heel=0 axis and is not allowed to go below zero.

i. The vertical position of the keel. The area is calculated from the hydrostatic sections used by Hydromax.Length.
Important note: heeling arm criteria dependent on displacement
Some heeling arm criteria are dependent on the displacement of the vessel for the calculation of the Heeling Arm. K. is assumed to be at the baseline (as set up in the Frame of Reference dialog). wind heeling etc.is manually calculated from:
A
.e. For example. λ0. For these types of heeling arms you should use the various heeling moment curves that are available – see below:
Heeling moment curves
Parent Heeling Moments
Heeling moments work the same way as the Minimum GM Calculations in that they can be cross referenced into criteria. The lateral projected area and its centroid of area are calculated for the upright vessel (zero heel) at the draft and trim defined in the loadcase or trim dialog. The advantage of using heeling moments is that they provide a constant heeling moment (varying heeling arm) as the vessel displacement changes (due to different loadcases or during a limiting KG analysis). is given by:
0
volHM StowFact
Where: volHM is the assumed volumetric heeling moment due to transverse grain shift in units of Length3. StowFact is the stowage factor in units of Length3/Mass.“Structure” surfaces are ignored. and is the vessel mass
Areas and levers
Some criteria require the evaluation of above and below water lateral projected areas and their vertical centroids. which take account of the vessel displacement as required. The user may also specify additional areas and vertical centroids or the total areas and vertical centroids. positive upwards. where
M = heeling moment Δ = displacement. In all cases the vertical centroids are given in the Maxsurf/Hydromax co-ordinate system. the value “A” in:
H( )
M
A cos n ( )
. These are in addition to the existing specific heeling arm curves for passenger crowding.: from the model‟s vertical datum. increasing the number of sections will increase the accuracy of the area calculation. even if the baseline does not correspond to the physical bottom of the vessel.
Page 240
.Appendix F
The heeling arm magnitude at zero heel. further. only “Hull” surfaces are included in the calculation . thus..

However. For wind n=2 is often used for heeling because both the projected area as well as the lever decrease with the cosine of the heel angle. D
C tan(
).
General cos+sin heeling moment
Some criteria. (mass. A is the magnitude of the heeling moment (mass. in this case n=0 should be used. require a heeling moment with both a sine and cosine component:
H( )
where:
k
A cos n ( )
B sin m ( )
is the heel angle.length) and (mass). such as IMO Severe wind and rolling (weather criterion) have a heeling arm of constant magnitude. the same heeling moment form may be used for computing towing heeling moments of the form:
H( )
k
A cos(
)
B sin(
)
in this case a constant angle (in the case of towing. It may be shown that this is equivalent to:
H( )
where:
k
C cos( )
D sin( )
C
R2 1 tan 2 (
) .
Typically n=1 is used for passenger crowding and vessel turning since the horizontal lever for the passenger transverse location reduces with the cosine of the heel angle. notably lifting of weights.Appendix B
The following heeling moments are available in the Hydromax criteria dialog:
General heeling moment General cos+sin heeling moment General heeling moment with gust User Defined Heeling Moment
General heeling moment
The general form of the heeling moment is given below. thus
the vessel displacement
A
is the magnitude of the heeling arm (length).length) and
A and B the magnitudes of the cosine and sine components of the heeling moment A B
the vessel displacement (mass). It should be noted that provided the n and m indices are both unity. It allows you to specify a constant heeling moment as opposed to a constant heeling arm:
H( )
where:
A
cos n ( )
is the heel angle. the angle of the tow above the horizontal) is included. R
2
A
2
B and
2
tan
B A
Page 241
. thus and
are the magnitude of the
heeling arm (length). some criteria.
cosn describes the shape of the curve.

User Defined Heeling Moment
With the User Defined Heeling Moment. Some criteria specify the ratio of the wind speeds.
Parent Stability Criteria
The parent criteria are divided up into different categories depending on their basic types.Appendix F
General heeling moment with gust
Some criteria require a Gust Ratio. A is the magnitude of the heeling moment (mass.
GustRatio
H gust H steady
The general form of the heeling moment is given below. if it is assumed that the wind pressure is proportional to the square of the wind seed.length) and (mass). thus
the vessel displacement
A
is the magnitude of the heeling arm (length).
It should be noted. the definition of gust ratio is the ratio of the heeling arms. Option The angle of Description Choose from the following (case insensitive auto-completion is used): Heel Pitch MaxSlope Units deg
Page 242
.
Criteria at Equilibrium
These criteria are calculated after an equilibrium analysis and relate to the equilibrium position of the vessel after the analysis. Trim or Slope at Equilibrium
This criterion may be used to check the value of maximum Heel. It allows you to specify a constant heeling moment as opposed to a constant heeling arm. Defining User Defined Heeling Moments works in much the same as for User Defined Heeling Arm. the ratio of the heel arms will be the square of the ratio of the wind speeds. Pitch or Maximum Slope (compared with an originally horizontal and flat deck).
Maximum value of Heel. the user can specify the number of points and the shape of the heeling moment curve. This heeling moment can then be linked into a Heeling arm criteria (xRef) for evaluation.
cosn describes the shape of the curve. this is the ratio of the magnitude of the wind heeling arm during a gust to the magnitude of the wind heeling arm under steady wind. The equilibrium criteria are only displayed in the report if you run an equilibrium analysis. that in this case.
H steady ( ) H gust ( )
where:
A A
cos n ( ) GustRatio cos n ( )
is the heel angle. Both the steady and the gust heel moment have the same shape.

use a combination of both forms of the minimum/maximum freeboard criteria.Appendix B
Shall be less than / Shall not be greater than
Permissible value
deg
Minimum Freeboard at Equilibrium
Checks whether the minimum freeboard is greater than a minimum required value. Option The value of Description Choose from the following (case insensitive auto-completion is used): Marginline DeckEdge DownfloodingPoints PotentialDfloodingPoints EmbarkationPoints ImmersionPoints Permissible value Units length
Shall be greater than / Shall not be less than
length
To check that the freeboard lies within a specified range. Option The value of Description Choose from the following (case insensitive auto-completion is used): Marginline DeckEdge DownfloodingPoints PotentialDfloodingPoints EmbarkationPoints ImmersionPoints Permissible value Units length
Shall be greater than / Shall not be less than
length
Maximum Freeboard at Equilibrium
Check that the maximum freeboard is less than a maximum required value. Option The value of Description Choose from the following (case insensitive auto-completion is used): GMtransverse GMlongitudinal) Permissible value Units length
Shall be greater than / Shall not be less than
length
GZ Curve Criteria (non-heeling arm)
These criteria. are calculated from the Large Angle Stability analysis in Hydromax.
Page 243
. This could be used to check that an embarkation point is sufficiently close to the waterline. This could be used to check margin line or downflooding point immersion.
Value of GMT or GML at Equilibrium
This criterion is used to check that the GM (transverse or longitudinal) exceeds a specified minimum value. calculated from the GZ curve.

The criterion is passed if the value of GMt is greater then the required value.Appendix F
Value of GMt at
Finds the value of GMt at either a specified heel angle or the equilibrium angle. If all the upper limit values are less than the lower limit. the greater of the following: User specified heel angle See Nomenclature
Units
deg
. The criterion is passed if the value of GZ is greater then the required value. the upper range heel angle specified in the criterion. Option in the range from the greater of specified heel angle angle of equilibrium
Page 244
Description Value of maximum GZ Lower limit for heel angle range. In addition to a fixed required value. angle of maximum GZ or the downflooding angle. This functionality is to allow criteria such as “The maximum GZ at 30deg or greater”. Option specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle Shall be greater than / Shall not be less than
Value of Maximum GZ
Description Value of GZ at either User specified heel angle See Nomenclature See Nomenclature See Nomenclature Permissible value
Units deg deg deg deg length
Finds the maximum value of GZ within a specified heel angle range. first peak in GZ curve. they will be ignored when selecting the lowest. If you want to check the value of GZ at a certain angle you can set both specified angles as the required angle. Note: Upper limit and analysis heel angle range It is required that the range of heel angles specified for the Large Angle Stability analysis is equal. then the criterion will fail. you may also select a calculation to provide the required minimum GM. or exceeds. Option specified heel angle angle of equilibrium Select calculation from list Shall be greater than / Shall not be less than
Value of GZ at
Description Value of GMt at either User specified heel angle See Nomenclature Chose a calculation for the minimum required GM from a copy of one of the Parent calculations Permissible value
Units deg deg length
length
Finds the value of GZ at either a specified heel angle. The criterion is passed if the value of GZ is greater than the required value. If any of the calculated angles for the upper limit are less than the lower limit. GMt is computed from waterplane inertia and immersed volume (not the slope of the GZ curve as this is inaccurate if the heel angle resolution is insufficient).

see graph below. The required GZ value depends on the angle at which the maximum occurs. Otherwise the value of maximum GZ is calculated. the lesser of the following: User specified heel angle. the required value of GZ is constant and is taken at this specified angle. This is 0 . Option heel angle at which required GZ is constant Description If the angle of maximum GZ is greater than or equal to this value. Units deg
Page 245
.Appendix B
to the lesser of specified heel angle
angle of first GZ peak angle of maximum GZ first downflooding angle Shall be greater than / Shall not be less than
Upper limit for heel angle range. See Nomenclature See Nomenclature See Nomenclature Permissible value
deg
deg deg deg length
Value of Maximum GZ Value of GZ at Specified Angle or Maximum GZ below Specified Angle
If the angle at which maximum GZ occurs is greater than a specified value. this should normally be specified and be less than or equal to the upper limit of the range of heel angles used for the Large Angle Stability analysis. the value of GZ at the specified angle is calculated. Otherwise the required value of maximum GZ varies as a hyperbolic function with the angle of maximum GZ.

Appendix F
Option required value of GZ at this angle is limited by first GZ peak angle limited by first downflooding angle Shall be greater than / Shall not be less than If If
GZ max 0
Description Required value of GZ at the heel angle specified above.
Units length deg
deg length
then GZ
0
must be greater than the specified. constant value. Angle at which GZ is measured may be limited to the location of the first peak in the GZ curve. Permissible value.80665m/s2 g GZ is the righting lever.
Variation of required GZ with angle of maximum GZ
The angle at which the GZ was measured is listed in the results. This is GZ 0 . measured and compared.
Page 246
.
0 GZ max
GZ max
0
then GZ max must be greater than
GZ
0
where: is the specified angle at which the required GZ value becomes a constant 0
GZ max
is the heel angle at which the maximum GZ of value occurs
0
GZ
is the GZ value at
0
and GZ max is the maximum value of GZ.
Value of RM at Specified Angle or Maximum RM Below Specified Angle
As above (Value of GZ at specified angle or maximum GZ below specified angle) except the righting moment rather than the righting lever is specified. Angle at which GZ is measured may be limited to first downflooding angle. The righting moment RM is given by:
RM
gGZ
where: is the vessel volume of displacement is the density of the liquid the vessel is floating in is acceleration due to gravity = 9.

The criterion is passed if the ratio is less then the required value. the lesser of specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle Shall be less than / Shall not be greater than
Description Ratio of GZ values at phi1 and phi2 First heel angle. the lesser of the following: User specified heel angle See Nomenclature See Nomenclature See Nomenclature Permissible value
Units
deg deg deg deg
deg deg deg deg %
Ratio of GZ values at phi1 and phi2
Page 247
. the lesser of specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle Phi2. second heel angle. first heel angle.Appendix B
Ratio of GZ Values at Phi1 and Phi2
Calculates the ratio of the GZ values at two specified heel angles. the lesser of the following: User specified heel angle See Nomenclature See Nomenclature See Nomenclature Second heel angle.
Ratio
Option
GZ GZ
1 2
Phi1.

immersion point). If the ratio is less than the required value.Appendix F
Angle of Maximum GZ
Finds the angle at which the value of GZ is a maximum positive value. The criterion is passed if the angle is greater then the required value. heel angle angle of margin line immersion angle of deck edge immersion first flooding angle of the angle of first GZ peak angle of max. The user may choose the type of Key point to define the downflooding angle (downflooding point.g. heel angle can be limited by first peak in GZ curve and/or first downflooding angle. GZ angle of vanishing stability Shall be less than / Shall not be greater than Description Ratio of equilibrium angle to the lesser of: Specified heel angle Angle of first immersion of the margin line Angle of first immersion of the deck edge Smallest immersion angle of the specified type of Key Point Angle of first local peak in GZ curve Angle at which maximum GZ occurs Angle of vanishing stability Permissible value Units deg deg deg deg deg deg deg %
Page 248
. Using a ratio gives more flexibility. e. The criterion is passed if the equilibrium angle is less then the required value. the user is advised that the vessel should be heeled in the opposite direction and the criterion is failed. then the criterion is passed. Option Shall be less than / Shall not be greater than Description Angle of equilibrium Permissible value Units deg
Ratio of equilibrium heel angle to the lesser of
The equilibrium angle and the lesser of the selected angles are compared. potential downflooding point. embarkation point. If the equilibrium angle is negative. Option limited by first GZ peak angle limited by first downflooding angle Shall be greater than / Shall not be less than
Angle of Equilibrium
Description Angle of maximum GZ The angle of maximum GZ shall not be greater than the angle at which the first GZ peak occurs The angle of maximum GZ shall not be greater than the angle at which the first downflooding occurs Permissible value
Units deg
deg
deg
Finds the angle of equilibrium from the intersection of the GZ curve with the GZ=0 axis.: it is possible to check that the equilibrium angle does not exceed half (or any other fraction) the downflooding angle. Option spec.

Option Shall be less than / Shall not be greater than Description Angle of vanishing stability Permissible value Units deg
Range of Positive Stability
The angular range for which the GZ curve is positive is computed. Option Shall be greater than / Shall not be less than Description Angle of margin line immersion Permissible value Units deg
Angle of Deck Edge Immersion
Finds the first/minimum angle at which the deck edge immerses. but this can be allowed to increase to 17 degrees if the deck edge is not immersed. Option Shall be greater than / Shall not be less than Description Angle of downflooding Permissible value Units deg
Angle of Margin Line Immersion
Finds the first/minimum angle at which the margin line immerses. The criterion is passed if the angle of vanishing stability is greater then the required value.
Angle of Downflooding
Finds the angle of first downflooding.Appendix B
Equilibrium heel angle satisfies either
This criterion is nothing more than two “Ratio of equilibrium heel angle to the lesser of” criteria. The actual criterion is passed if either of the individual criteria is passed. Option Shall be greater than / Shall not be less than Description Angle of deck edge immersion Permissible value Units deg
Angle of Vanishing Stability
Finds the angle of vanishing stability from the intersection of the GZ curve with the GZ=0 axis. The criterion is passed if the computed range is greater then the required value. The criterion is passed if the smallest angle at which the margin line immerses is greater then the required value. Option from the greater of Description Range of positive stability Lower limit Units
Page 249
. This type of criterion is used to formulate criteria such as: The maximum allowable angle of equilibrium is 15 degrees in the damage condition. The criterion is passed if the downflooding angle is greater then the required value. The criterion is passed if the smallest angle at which the deck edge immerses is greater then the required value.

angle above equilibrium angle of first GZ peak angle of maximum GZ first downflooding angle immersion angle of Marginline or DeckEdge angle of vanishing stability Shall be greater than / Shall not be less than Description GZ area between limits type 1 .angle
Page 250
.standard Lower limit for integration.Appendix F
Option specified heel angle angle of equilibrium to the lesser of first downflooding angle angle of vanishing stability Shall be greater than / Shall not be less than
Description User specified heel angle See Nomenclature Upper limit of the range See Nomenclature See Nomenclature Permissible value
Units deg deg deg deg deg
GZ Area between Limits type 1 . from greatest angle of User specified heel angle See Nomenclature Upper limit of integration.standard
The area below the GZ curve and above the GZ=0 axis is integrated between the selected limits and compared with a minimum required value. from lesser angle of User specified heel angle User specified heel angle above the equilibrium heel angle See Nomenclature See Nomenclature See Nomenclature See Nomenclature Units
deg deg
deg deg deg deg deg deg
See Nomenclature Permissible value
deg length. Option from the greater of specified heel angle angle of equilibrium to the lesser of specified heel angle spec. The criterion is passed if the area under the graph is greater than the required value.

However the required minimum area depends on the upper integration limit. required area = A1 .749(18) §4.07 0.055 30 30 15
max
max
or simplifying:
0. then the required area would be given by:
A
A
0.36(63) §2.55 0.
and A2 is the
For example. The criterion is passed if the computed area under the graph is greater then the required value.001 30
Page 251
. The required area is defined below and is based on the area required for IMO MSC.5.standard GZ area between limits type 2.055m.rad.Appendix B
GZ area between limits type 1 .2 and IMO A.HSC monohull type
The area under the GZ curve is integrated between the specified limits. The required area is defined as follows: If If
max max 2
: required area = A2 .
A1 is the area under the GZ curve required at the specified lower heel angle
area under the GZ curve required at the specified higher heel angle
2.07m.
the upper integration limit.1.
1.55
0.6.
1:
A2
If 1 Where:
max is max 2
A1
2
A2
2 1 max
: required area =
.3.3. if the lower angle was 15 and the required area at this angle was 0.2.rad and the upper angle was 30 and the required area at this angle was 0.

HSC monohull type Lower limit for integration.. from smallest angle of User specified heel angle User specified heel angle above the equilibrium heel angle See Nomenclature See Nomenclature See Nomenclature See Nomenclature Minimum angle that requires a GZ area greater than. Until this angle the required GZ area is constant Value of GZ area that is required until the lower heel angle Angle from which the required GZ area remains constant onwards Value of GZ area that is required from the higher heel angle onwards Permissible value
Units
deg deg
deg deg deg deg deg deg deg
required GZ area at lower heel angle higher heel angle required GZ area at higher heel angle Shall be greater than / Shall not be less than
length.Appendix F
Variation of required area with upper integration limit
Option
from the greater of specified heel angle angle of equilibrium to the lesser of specified heel angle spec. angle above equilibrium angle of first GZ peak angle of maximum GZ first downflooding angle angle of vanishing stability lower heel angle
Description GZ area between limits type 2.angle
Page 252
. from greatest angle of User specified heel angle See Nomenclature Upper limit of integration.angle deg length.angle length..

1.055 30 /
max
Page 253
. The criterion is passed if the computed area under the graph is greater than the required value.055m.rad. then the required area would be given by:
A
0. However the required minimum area depends on the upper integrationA1 1 / max).1.
the upper integration limit. The required area is defined below limit ( and is based on the area required for IMO MSC.HSC monohull type GZ area between limits type 3 .HSC multihull type
The area under the GZ curve is integrated between the specified limits. if the specified angle ( 1 ) was 30 and the required area at this angle ( A1 ) was 0.36 (63) Annex 7 §1. required area = A1 Where:
max is
1
/
max
.
A1 is the area under the GZ curve required at the specified heel angle
For example.Appendix B
GZ area between limits type 2 .

Ratio of GZ area between limits – Example 1
In the following example the upper limit for Area 1 has been set to the downflooding angle. The limits for Area 2 remain unchanged.Appendix F
Option Area 2 to specified heel angle Shall be greater than / Shall not be less than
Description Area 1 upper integration limit. respectively and the limits for Area 2 are vanishing stability and 180 deg.
Page 256
. see graph below. User specified heel angle Permissible value
4
Units deg %
This criterion is designed to be calculated on the positive side of the GZ curve only. Typically. GZ areas below the GZ=0 axis on the negative heel angle side of the GZ curve are not considered positive. Area 1 would be from equilibrium to vanishing stability and Area 2 would be from vanishing stability to 180 deg. In the example below. the lower and upper integration limits for Area 1 are equilibrium and vanishing stability.

Note that Area 2 is now A1 – A2.
Ratio of GZ area between limits – Example 3 Ratio of positive to negative GZ area between limits
This criterion calculates the ratio of GZ area above the GZ=0 axis to that below the axis in the given heel angle range.Appendix B
Ratio of GZ area between limits – Example 2
In the final example. Option Description Units
Page 257
. the lower integration range for Area 2 has been reduced to the downflooding angle.

Page 258
. where the value of GZ < 0. Positive heel: lower limit = 0deg.
If both heel angle limits are < zero: Area 1 is the total area between the GZ curve and GZ=0 axis. Area 1 is positive. Area 2 is negative. where the value of GZ > 0.Appendix F
Option
in the heel angle range from to Shall be greater than / Shall not be less than
Description Ratio of positive to negative GZ area between limits User specified lower limit heel angle User specified upper limit heel angle Permissible value
Units
deg deg %
Ratio =
Area 1 . where the value of GZ < 0. Area 2 is negative. upper limit = 180deg. Area 2 is the total area between the GZ curve and GZ=0 axis. Area 2 is the total area between the GZ curve and GZ=0 axis. And the areas are defined as follows: If both heel angle limits are ≥ zero: Area 1 is the total area between the GZ curve and GZ=0 axis. where the value of GZ > 0. abs Area 2
where “abs” means the absolute value of. Area 1 is positive.
Ratio of positive to negative GZ area between limits.

Appendix B
Ratio of positive to negative GZ area between limits. Area 1 is positive. where the value of GZ < 0 for heel angles < 0. Negative heel: lower limit = -180deg. and the upper heel angle limit > zero (the upper limit is assumed to be greater than the lower limit): Area 1 is the total area between the GZ curve and GZ=0 axis.
Ratio of positive to negative GZ area between limits. Positive and negative heel: lower limit = -180deg. where the value of GZ > 0 for heel angles ≥ 0 plus the area between the GZ curve and GZ=0 axis.
If the lower heel angle limit < zero. Area 2 is negative. where the value of GZ < 0 for heel angles ≥ 0 plus the area between the GZ curve and GZ=0 axis. upper limit = 180deg. where the value of GZ > 0 for heel angles < 0.
Page 259
. Area 2 is the total area between the GZ curve and GZ=0 axis. upper limit = 0deg.

except for the fact that you don‟t have to specify the heeling arm for each criterion separately.5 GZmax . GZ limit Range limit
deg deg deg deg deg deg deg length deg
S = C sqrt( 0. User specified heel angle See Nomenclature The lowest of the selected angles is be to specify the upper limit of the range of positive stability and the range in which the maximum value of GZ should be found. these can be cross-referenced into new heeling arm criteria:
Page 260
.MSC 19(58)
Probabilistic damage s-factor according to MSC 19(58) Option Lower angle of range : the greater of Description The greater of the selected angles is be to specify the lower limit of the range of positive stability and the range in which the maximum value of GZ should be found. angle above equilibrium angle of first GZ peak angle of maximum GZ first downflooding angle immersion angle of Marginline or DeckEdge angle of vanishing stability Max. The criteria themselves work much the same as the Heeling arm criteria (page 264). After you have defined your heeling arms. but can simply select which heeling arm you wish to apply.Appendix F
Subdivision Index s-factor .
Heeling arm criteria (xRef)
The cross-reference heeling arm criteria are set up to allow you to define heeling arms or heeling moments in a central location and then cross-reference or link them into the criteria. range) Both the values of maximum GZ and range of positive stability can be clipped. See Nomenclature See Nomenclature See Nomenclature See Nomenclature See Nomenclature See Nomenclature See Nomenclature Upper limit of allowable maximum GZ value when computing s Upper limit of allowable range of positive stability when computing s Units
specified heel angle angle of equilibrium Upper angle of range: lesser of
deg deg
specified heel angle spec.

25 B
0. required GM
Page 261
. is calculated as follows:
GM
L B Vd 0.23(59).Appendix B
The heeling arms are cross-referenced simply by selecting the desired heeling arm from the pull-down list:
For information on defining heeling arms or moments.645 B Vd
0. see Minimum GM calculator – Grain The required GM for vessels carrying grain. as defined in IMO Resolution MSC.0875 SF
Where (using consistent units): L is the combined length of all full compartments B is the moulded breadth of the vessel SF is the stowage factor Vd is the calculated average void depth Δ is the vessel displacement
Input parameters for: Grain heeling min.

0033 Ton/ft2 and k1 = 14200 ft4/Ton k0 = 0. Δ is the vessel displacement 0 is a critical heel angle which may be a fixed angle or a fraction of the deck-edge or marginline immersion angle A is the windage area which may be specified as a total area or as an area additional to the area of the hull above the waterline. h is height of the centroid of A above the zero point.036 t/m2 and k1 = 1309 m4/t For CFR 46.170: ocean service: k0 = 0. 170.170: service on partially protected water: k0 = 0.170: service on protected water: k0 = 0.028 t/m2 and k1 = 1309 m4/t
Input parameters for: Wind pressure min. 170. H is the height of the assumed centre of lateral resistance of the vessel.Appendix F
Minimum GM calculator – Wind pressure
The GM required to withstand wind pressure is calculated as follows:
k0 GM
L k1
2
A(h H ) cos n ( 0 ) sin( 0 )
Where (using consistent units): L is the waterline length of the vessel (if the criterion required LPP or LOA then enter the value directly rather than having it calculated by Hydromax.005 Ton/ft2 and k1 = 14200 ft4/Ton k0 = 0. 170. required GM Minimum GM calculator – Constant
The required GM is calculated as follows:
GM
a cos n ( 0 ) sin m ( 0 )
Where (using consistent units): a is a constant arm or moment (depending on whether the vessel displacement is used) 0 is a critical heel angle which may be a fixed angle or a fraction of the deck-edge or marginline immersion angle
Page 262
. k0 and k1 are constants. for example: For CFR 46.0025 Ton/ft2 and k1 = 14200 ft4/Ton k0 = 0.055 t/m2 and k1 = 1309 m4/t For CFR 46.

Parent Heeling Arms on page 229. required GM Minimum GM calculator – Constant with freeboard
The required GM is calculated as follows:
GM
a f
B fa
cos n ( 0 ) sin m ( 0 )
Where (using consistent units): a is a constant arm or moment (depending on whether the vessel displacement is used) B is the vessel beam f is the minimum freeboard for the upright (zero heel) condition to the deck-edge or marginline. a heel adjustment may be included: 0 is a critical heel angle which may be a fixed angle or a fraction of the deck-edge or marginline immersion angle m. 171. typically the height of the watertight trunk l is a length. b is their average transverse location and K is the number of passengers per unit mass. n are the exponents for sine and cosine.050:
GM
Nb with a K tan( 0 )
Nb and m. fa is the additional freeboard allowance calculated as follows (additionally the freeboard allowance may be limited to a maximum specified value):
fa
k h
l L
2b b0 B
b1
Where (using consistent units): L is the waterline length of the vessel (if the criterion required LPP or LOA then enter the value directly rather than having it calculated by Hydromax.Appendix B
m. n = 1. typically the length of the watertight trunk b is a breadth.
Input parameters for: Constant min. An example of where this calculation should be used is in CFR 46.0 K
Where N is the number of passengers. typically the breadth of the watertight trunk b0 is a constant with the same units as b b1 is a dimensionless constant If desired.
Page 263
. n are the exponents for sine and cosine. B is the same as that used in the expression for GM k is a dimensionless constant h is a height.

angle of deck edge immersion. they only exist in xRef form. combined criteria. This is because a wider range of heeling arm formulations is available and for some criteria.Appendix F Heeling arm criteria
The preferred method is to use the xRef heeling arm criteria rather than the stand alone heeling arm criteria. The criterion is passed if the GZ value is greater then the required value. In addition. The heeling arm criteria available in the Hydromax Criteria dialog are listed below.
Page 264
. The specified cross-referenced heel arm is then evaluated at this heel angle to give: HA( ) . these are where several criteria are applied to the same heeling arm
Value of GMT at equilibrium . The criterion is passed if the GMT value is greater then the required value. The transverse GM is taken at a user-specified heel angle or angle of equilibrium (without heel arm). Also available are:
Multiple heeling arm criteria. these are where the same criterion is applied to up to three heeling arms and/or combinations of these heeling arms Heeling Arm. GMT is computed from the waterplane inertia and the displaced volume at the equilibrium heel angle. or first flooding angle of the specified key point type.general heeling arm
Calculates the transverse metacentric height (GMT) at the intersection of the GZ and heel arm curves.general heeling arm
Calculates the value of the GZ curve at the equilibrium intersection of the GZ and heel arm curves.
Ratio of GMT and heeling arm
Calculates the following ratio and the criterion is passed if the ratio exceeds the specified value. Finally.
GM sin( )
HA( )
Where the heel angle.
Ratio of GMt and heel arm criterion Value of GZ at equilibrium . is the lesser of: a user-specified heel angle. angle of margin line immersion. this angle may also be multiplied by a user-specified factor. .

general heeling arm Value of maximum GZ above heeling arm
Finds the maximum value of (GZ .heel arm) at or above a specified heel angle.
Page 265
. The criterion is passed if the value of (GZ .heel arm) is greater then the required value. The first downflooding angle may be selected as an upper limit.Appendix B
Value of GZ at equilibrium .

5 ).0) will be selected. However this option would normally be used to specify an upper limiting angle of “half the angle of margin line immersion”.
Maximum ratio of GZ to heeling arm
This criterion calculates the maximum ratio of GZ : Heeling arm (for the same heel angle) within the range of heel angles specified. including “specified heel angle”. the maximum ratio of GZ:heel arm occurs at 21.Appendix F
Value of maximum GZ above heeling arm
The upper limit may be specified as a certain percentage of the selected limits. then the point with maximum positive GZ (where the heeling arm 0. Examples:
Upper limit is 50% of angle of margin line immersion (43 / 2 = 21. The value of GZ at this heel angle must be greater than zero. In the range 0 to 21. If the heeling arm is zero or negative in the range. This is applied to all selected upper angle limits. This is applied to all selected upper angle limits. including “specified heel angle”.
Page 266
. The upper limit may be specified as a certain percentage of the selected limits.930m giving a ratio of 59%.5 .5 . At this heel angle the value of GZ is 0. However this option would normally be used to specify an upper limiting angle of “half the angle of margin line immersion”.553m and the heel arm 0.

5m giving a ratio of 224%.)
Page 267
. the downflooding angle is 94. The angle and value of GZ is given for the location where it is a maximum (in the region where the heel arm is zero.Appendix B
In this case a constant heeling arm is used. the exact value will depend slightly on the heel angles tested in the Large Angle Stability analysis.122m and the heel arm 0. thus the maximum ratio occurs at the angle of maximum GZ (62. At this heel angle the value of GZ is 1.
Finally. Hence the criterion is passed.4 ). at this heel angle the heel arm is zero (thus the ratio infinite).3 .

Appendix F
The same is true if an unusual user-defined heeling arm is used. The heel arm is used to define the equilibrium angle and the heel angle where (GZ .
GZ Ratio = GZ
1 2
Angle of maximum GZ above heeling arm
Calculates the heel angle at which the difference between the GZ curve and the heeling arm is greatest (GZ . positive). The criterion is passed if the ratio is less than the required value. This criterion can be used to check that the GZ is at least as great as the heeling arm over the specified range. The criterion is passed if the angle is greater then the required value. Minimum ratio of GZ to heeling arm
This criterion calculates the minimum ratio of GZ : Heeling arm (for the same heel angle) within the range of heel angles specified. However this option would normally be used to specify an upper limiting angle of “half the angle of margin line immersion”. This is applied to all selected upper angle limits.
Page 268
.Heel Arm is maximum. The upper limit may be specified as a certain percentage of the selected limits. including “specified heel angle”.general heeling arm
Used to check the ratio of GZ values at two points on the GZ curve. In this case the heeling arm is zero between 50 and 70 . And checks that this ratio is greater than a specified value.
Ratio of GZ values at phi1 and phi2 . Hence the maximum ratio reported is infinity and occurs at the angle where GZ is maximum in this heel angle range.heel arm) is maximum. the same criterion may be used to check that the GZ is positive over the specified range. If a heeling arm with zero amplitude is used.

The criterion is passed if the equilibrium angle is less then the required value.Appendix B
Angle of maximum GZ above heeling arm . The equilibrium angle is the smallest positive angle where the GZ and heeling arm curves intersect and the GZ curve has positive slope.general heeling arm
Page 269
.
Angle of equilibrium .general heeling arm
Calculates the angle of equilibrium with the specified heeling arm.general heeling arm Angle of equilibrium .

general heeling arm
Calculates the ratio of the angle of equilibrium (with the specified heeling arm) to another. Ratio =
equilibriu m specified
The other angle used to compute the ratio may be one of the following: Required angle for ratio calculation Auto complete text Marginline immersion angle MarginlineImmersionAngle Deck edge immersion angle DeckEdgeImmersionAngle Angle of first GZ peak DownfloodingAngle Angle of maximum GZ MaximumGZAngle First downflooding angle FirstGZPeakAngle Angle of vanishing stability with heel arm VanishingStabilityWithHeelArmAngle
Angle of vanishing stability .general heeling arm Range of positive stability . The criterion is passed if the angle is greater then the required value. selectable angle.Appendix F
Angle of equilibrium ratio . [Range of stability] = [Angle of vanishing stability] – [Angle of equilibrium] The criterion is passed if the value of range of stability is greater then the required value.
Angle of vanishing stability .general heeling arm
Calculates the location of the first intersection of the GZ curve and heel arm curve where the slope of the GZ curve is negative.general heeling arm
Computes the range of positive stability with the heeling arm. This criterion should not be confused with the range of positive stability. The angle of equilibrium is computed as described in §Angle of equilibrium general heeling arm.
Page 270
.

general heeling arm
Computes the area below the GZ curve and above the heel arm curve between the specified heel angles. The criterion is passed if the area is greater than the required value.Appendix B
Range of positive stability .general heeling arm GZ area between limits type 1 .
2
Area =
GZ ( ) heel arm( ) d
1
GZ area between limits type 1 .general heeling arm
Page 271
.

Appendix F
GZ area between limits type 2 .
2
Area 1 = Area 2 =
GZ ( ) heel arm( ) d
1
.general heeling arm
The ratio of the area between the GZ curve and heel arm and the area under the GZ curve is computed.
Area 1 constant kArea 2
GZ area between limits type 2 .general heeling arm Ratio of areas type 1 .
2
Area 1 = Area 2 =
GZ ( ) heel arm( ) d
1
.general heeling arm
The area between the GZ curve and heel arm and the area under the GZ curve is computed (Area 1). The required value is based on a constant plus a proportion of the area under the GZ curve (Area 2).
4 3
GZ ( )d
.
Page 272
. The criterion is passed if the ratio is greater than the required value.
4 3
GZ ( )d
. This criterion is based on the area ratio required by various Navies‟ turning and passenger crowding criteria. Type 1 stands for which areas are being integrated to calculate the ratio (see graph). The criterion is passed if the ratio is greater than the required value.

0 is used. For more information see: §Heel.Appendix B
Area 1 Ratio = Area 2
Ratio of areas type 1 . then roll to leeward under a gust. Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. but the integration for Area 1 is taken from the equilibrium with the gust wind heeling arm.general heeling arm
This criterion is used to simulate the effects of wind heeling whilst the vessel is rolling in waves.e.general heeling arm Ratio of areas type 2 . The roll back may be specified as either a fixed angular roll back from the angle of equilibrium with the steady wind heel arm or can be rolled back to the vessel equilibrium angle ignoring the wind heeling arms (i.
2
Area 1 = Area 2 =
GZ ( ) gust heel arm( ) d
gust heel arm( ) GZ ( ) d
Page 273
1
2 1
. Because of the many different ways in which this criterion is used it has several options for defining the way in which the areas are calculated.: where the GZ curve crosses the GZ=0 axis with positive slope). If a gust ratio of greater than 1. the vessel is assumed to roll to windward (under the action of waves with the steady wind pressure acting on it. Hence the rollback angle is taken from the equilibrium angle with the steady wind heeling arm.

general heeling arm
The ratio of the area under the GZ curve to the area under the heel arm curve is computed.Appendix F
Area 1 Ratio = Area 2
Ratio of areas type 2 . This criterion is based on the area ratio required by BS6349-6:1989.
2 1
heel arm( )d .
Area GZ Area HA
Page 274
. Area GZ = Area HA = Ratio =
2 1
GZ ( )d .general heeling arm Ratio of areas type 3 . The criterion is passed if the ratio is greater than the required value. Areas under the GZ=0 axis are counted as negative.

general heeling arm
Multiple heeling arm criteria
These criteria are used to check the effects of combinations of up to three heeling arms and their combinations.general heeling arm with the specified heeling arms.
Ratio of GZ values at phi1 and phi2 .Appendix B
Ratio of areas type 3 . for example passenger crowding. wind.
Page 275
. turning.multiple heeling arms
Checks the ratio of GZ values as per §Ratio of GZ values at phi1 and phi2 . The combined heeling arms are computed by adding the values of the individual heeling arms at each heel angle.

then only the s-Final factor is computed and in this case. respectively.length
Vessel type: If Passenger is selected. then all three s-factors are computed as for the Passenger ship. The area ratio must be greater than a specified value. combined criteria
Several criteria require the evaluation of several individual criteria components. Angle of steady heel must be less than a specified value.general heeling arm. These are: 1. {GZmax / limitGZmax . Note: At least one of the individual criteria has to be selected.
Combined criteria (ratio of areas type 1) .
Page 281
. Range / limitRange}1/4 if equilibrium heel > Max. and any values for the s-Final factor minimum and maximum heel angles may be specified. For the s-Final factor. The Angle of steady heel is obtained as per §Angle of equilibrium . 2. If Cargo is selected. Although it is possible to evaluate these criteria by evaluation of their individual components. the minimum and maximum heel angles are set to 7 and 15 deg. All s-factors are in the range 0 <= s <= 1
Heeling arm.length mass. The ratio of the value of GZ at equilibrium to the value of maximum GZ must be less than a specified value. allowable equilibrium heel angle then s-Intermediate = 0 s-Moment = (GZmax – GZ reduction) .general heeling arm
This is a combined criterion where three individual criteria must be met. for simplicity the common combinations have been combined into single criteria. The criterion result is then the minimum value of s-Intermediate and (s-Final * s-Moment). Displacement / Mheel where: Mheel is the maximum of the three selected heeling moments. the minimum and maximum heel angles are set to 25 and 30 deg. respectively. s-Final = K. The area ratio is evaluated as per § Ratio of areas type 1 . If User is selected.Appendix B
moment Wind heel moment Select survival craft heel moment Shall be greater than / Shall not be less than Link to wind heeling moment Link to heeling moment that defines the effect of launching survival craft Permissible minimum value for sfactor mass.general heeling arm 3. The result is the minimum of s-Intermediate and (s-Final * s-Moment). then s-Intermediate and s-Moment factors are computed. Range / limitRange}1/4 where: K = 1 if equilibrium heel <= Theta_min K = 0 if equilibrium heel >= Theta_max K = {(Theta_max – equilibrium heel) / (Theta_max – Theta_min)}1/2 s-Intermediate = {GZmax / limitGZmax .

Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle.general heeling arm.
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. 2. 1. For more information see: §Heel. Optionally. The angle of steady heel is obtained as per Angle of equilibrium . The area ratio is evaluated as per Ratio of areas type 2 .Appendix F
Combined criteria (ratio of areas type 1) .general wind heeling arm
This is a widely applicable wind heeling criterion in its most generic format. The area ratio must be greater than a specified value. The heeling arm is specified simply by a magnitude and cosine power. 3. a gust wind can be applied.general heeling arm Combined criteria (ratio of areas type 2) . The ratio of the value of GZ at equilibrium to the value of maximum GZ must be less than a specified value.general heeling arm. Angle of steady heel must be less than a specified value.

Appendix B
Area definition
If required. If this is done. all calculations are done using a reduced GZ‟ curve which is computed at each heel angle as follows:
GZ ' ( )
GZ ( ) B cos m ( )
This criterion may be used to evaluate the following specific criteria (as well as many others of similar format):
Page 283
. a reduction of the GZ curve may be applied.

The heeling arm is normally derived from a GZ value. fixed heel angle
Units
Area1 integrated from the greater of (phi1) spec. the magnitude of the heeling arm is derived (rather than specified directly) from a required relationship between the GZ curve and the heeling arm curve.Appendix B
Option
Description Combined criteria (ratio of areas type 2a) Angle that defines the lower heel angle for the integration range of Area1. The required ratio of Area3/Area2 used to determine the angle phi3
deg
deg deg
deg
angle at which Area3 / Area1 is
deg
Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. The GZ value used to define the heeling arm is the GZ at one of the following heel angles:
Page 285
. phi3 may be determined from a number of features of the GZ curve including being chosen such that Area3/Area1 is some specified value. The criterion is then evaluated by comparing some requirement of the derived heeling arm with a specified value. The shape of the heeling arm (e. heel angle (equilibrium angle during lifting) roll back from angle of equilibrium with heeling arm angle of equilibrium (without heel arm) Area2 integrated to the lesser of (phi2) Max. cos1. heeling angle due to roll taken as the lesser of (phi3)
deg
A roll-back angle (positive) from the angle of equilibrium with the heeling arm (first up-crossing intersection of the GZ and heeling arm curves) Roll back to the angle of equilibrium of the vessel (ignoring the heeling arm) Upper integration limit of Area2 chosen from the lesser of the seven options.3) must be specified. The lesser of the following three options A specified. This angle is used to evaluate the second part of the criterion: the difference phi2-phi3 must be greater than the required value.
Derived heeling arm criteria
For these criteria.g.
GZ derived heeling arm
This criterion is used to calculate the amplitude of a heeling arm derived from the value of GZ at a certain heel angle. For more information see: §Heel. GZ area or angle of equilibrium requirement.

Appendix F
specified angle of heel angle of first peak in GZ curve angle at which maximum GZ occurs angle of first downflooding immersion angle of margin line or deck edge
The heeling arm is then calculated as described by the equation below.
A
where:
GZ cos n
Amplitude of heeling arm Shape of heeling arm (n = 0 for constant heeling arm) Specified heel angle Value of GZ at specified heel angle Required ratio = GZ / HA
A n
GZ
GZ area derived heeling arm type 1
This criterion is used to calculate the amplitude of a heeling arm derived from the area under the GZ curve between specified limits.
2 2 1
GZ d
A cos n
d
1
A n
GZ
Amplitude of heeling arm Shape of heeling arm (n = 0 for constant heeling arm) heel angle GZ curve Required ratio
Page 286
.
1:
specified angle of heel angle of equilibrium
Upper integration limit. heel angle
2:
spec. see below. angle above equilibrium angle of first GZ peak angle of max. GZ first downflooding angle angle of vanishing stability
It is also possible to specify a minimum heel angle for the upper integration limit. which satisfies the equation below arm is then found and compared with a minimum required value. Any negative areas (due to negative GZ) up to this minimum upper integration heel angle will be deducted from the total area under the GZ curve. Lower integration limit.
spec. and is then compared with a minimum required value. The amplitude of the heeling. The area under both the GZ and heeling arm curves is integrated between the same specified limits.

The roll back may be specified as either:
a fixed angular roll back from the angle of equilibrium with the wind heel arm. the vessel is assumed to roll to windward under the action of waves and then roll to leeward. The amplitude of the heeling arm is then compared with a required minimum value. Because of the many different ways in which this criterion is used it has several options for defining the way in which the areas are calculated. The steady heel arm is derived from a gust of specified ratio.Appendix B
GZ area derived heeling arm type 2
This criterion is used to simulate the effects of wind heeling whilst the vessel is rolling in waves. roll back to the vessel equilibrium angle ignoring the wind heeling arms (i.general heeling arm Angle of equilibrium .
Page 287
. angle of the first GZ peak. For more information see: §Heel. The rollback angle is taken from the equilibrium angle with the wind heeling arm. The wind gust will cause the vessel to heel over to the lesser of a specified heel angle.: where the GZ curve crosses the GZ=0 axis with positive slope).
Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. A heeling arm of prescribed shape is found such that the specified area ratio is met.GZ derived wind heeling arm
The derived wind heeling criterion is used to check that the steady heel angle due to wind pressure exceeds a certain value. or roll back to a specified heel angle. angle of maximum GZ or the first downflooding angle. With the wind pressure acting on it. Area 1 =
2 1
GZ ( ) heel arm( ) d
Area 2 =
2 1
heel arm( ) GZ ( ) d
Area 1 Ratio = Area 2
GZ area derived heeling arm (type 2) .e.

This means that the lesser of: a specified heel angle. the same cosine power is used for both the specified and the derived heeling arms. angle of maximum GZ or the first downflooding angle.GZ area derived heeling arm
This criterion is used to compare the equilibrium angles with two different heeling arms.derived wind heeling arm Ratio of equilibrium angles . The first equilibrium angle. are in the specified ratio. The specified heeling arm is specified by an amplitude and cosine power. The derived heeling arm is chosen such that the areas. if the angle of steady heel is greater than the angle. is the angle of equilibrium with a specified heeling arm.
Page 288
. is the angle of equilibrium with a derived heeling arm. should be large enough to withstand a gust from a steady wind heeling angle larger than …. The second equilibrium angle. A1 and A2. first peak in GZ curve. There are several options which can be used to define the upper and lower ranges for the area integrations.
Angle of equilibrium .Appendix F
The vessel is assumed to be safe from gusts up to the specified ratio. φ2. φ1.

Units
AS. zero trim condition. Note that no additional windage areas are calculated by Hydromax for this criterion. this is not the same as the STIX variable hCE which is measured from the waterline. Hull beam as defined by ISO 8666. either 0 or 5.STIX
The stability index criterion or STIX criterion as described in ISO/FDIS 12217-2:2002(E) is used to assess the stability of sailing craft. has reserve buoyancy and positive righting lever at a heel angle of 90º 0 in all other cases. beam of hull
length
Page 290
. . Hull length as defined by ISO 8666.
Other combined criteria
Other criteria. Sail area as defined in ISO 8666. For more information see: §Heel. Hydromax calculates this parameter as the overall length of the vessel (all hull surfaces) in the upright. indicating that the equilibrium heel angle with the specified heel arm must be less than the equilibrium heel angle with the derived heel arm
Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. 5 if the vessel. which do not easily fall into the categories above. when fully flooded with water. This may be either specified or calculated by Hydromax. zero trim condition. This may be either specified or calculated by Hydromax. The required input parameters are described below. Option delta Description Adjustment to STIX rating. positive up). are found here.
Other criteria .Appendix F
required value
equilibrium with derived heel arm Specifies the maximum allowable ratio of equilibrium heel angle with the specified heel arm to the equilibrium heel angle with the derived heel arm (phi2 / phi1). Please refer to ISO/FDIS 12217-2:2002(E) for exact definitions of parameters and how they should be calculated. This value is normally less than or equal to 100%. Hydromax calculates this parameter as the overall beam of the vessel (all hull surfaces) in the upright. sail area ISO 8666
length2
height of centroid of AS
length
LH. Height of sail area centre of effort from model‟s vertical datum (not necessarily the waterline. length
length
BH.

This may be either specified or calculated by Hydromax. Hydromax calculates this parameter as the waterline length of the vessel (all hull surfaces) at zero heel and at the loadcase displacement and centre of gravity.
Page 291
. Hydromax uses the numerical STIX rating value rather than the STIX design category.passenger crowding heeling arm
Calculates the angle of equilibrium with the heeling arm due to passenger crowding applied. this is not the same as the STIX variable hLP ). Hydromax calculates this parameter at zero heel and at the loadcase displacement and centre of gravity. if the analysis is carried out freeto-trim. Hydromax calculates this parameter as the waterline beam of the vessel (all hull surfaces) at zero heel and at the loadcase displacement and centre of gravity. if no downflooding points are defined. This may be either specified or calculated by Hydromax. the angle of downflooding is taken to be the largest heel angle tested. the waterline of the trimmed vessel is used.Appendix B
Option LWL. but it is highly recommended to use the equivalent xRef criteria with the desired heeling arms. Note that a downflooding angle is required to calculate the STIX index.
Specific stand alone heeling arm criteria
These criteria provide some specific stand alone heeling arm criteria. length waterline
BWL.
Stand alone heeling arm criteria
Angle of equilibrium . beam waterline
height of immersed profile area centroid
Shall be greater than / Shall not be less than
Description Hull waterline length in the current load condition as defined by ISO 8666. see §Passenger crowding. Hence. The heeling arm is calculated from the number.
Units length
length
length
Hydromax calculates the various factors and STIX rating according to ISO/FDIS 122172:2002(E). or defined downflooding points do not immerse within the selected heel angle range. Height of centre of the lateral projected immersed area of the hull from model‟s vertical datum (not necessarily the waterline. if the analysis is carried out freeto-trim. the waterline of the trimmed vessel is used. if the analysis is carried out freeto-trim. weight and location of the passengers. This affects the calculation of the Wind Moment and Downflooding factors. the waterline of the trimmed vessel is used. may be specified or calculated by Hydromax. They are included for compatibility with criteria sets defined in earlier versions of Hydromax. Hull waterline beam in the current load condition as defined by ISO 8666.

This is used to simulate the effects of lifting weights and is used by several Navies.general heeling arm except that the heel arm has both a cos and sin component. vessel speed and height of the vessel‟s centre of gravity.
Combined criteria (ratio of areas type 1) .
Combined criteria (ratio of areas type 1) . see §Turning. the only difference being the shape of the heel arm.Appendix F
Angle of equilibrium . The heeling arm is calculated from the turn radius.passenger crowding
This criterion is essentially the same as its generic form: Combined criteria (ratio of areas type 1) .general cos+sin heeling arm
This is a very similar criterion to § Ratio of areas type 1 . however the heel arm is the specific passenger crowding form. for further information also see §General cos+sin heeling arm
H( )
Area 1 = Area 2 =
k A cos n ( )
2 1
B sin m ( )
.high-speed turn
This criterion is essentially the same as its generic form: Combined criteria (ratio of areas type 1) .high-speed turn heeling arm
Calculates the angle of equilibrium with the heeling arm due to high speed turning applied.
Ratio of areas type 1 . In this criterion the heel arm has both a sine and a cosine component.
Page 292
. however the heel arm is the specific high-speed turning form.
GZ ( ) heel arm( ) d
4 3
GZ ( )d
.general heeling arm.
Area 1 Ratio = Area 2
Stand alone heeling arm combined criteria
Combined criteria (ratio of areas type 1) . The modified form of the heeling arm is given below.general heeling arm.general cos+sin heeling arm
The lifting criterion is the same as the Combined criteria (ratio of areas type 1) .general heeling arm.

For more information see: §Heel.Appendix F
Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle.
Page 294
.

from this we can deduce that the value of GZ and Heeling arm are the same at these angles. In Hydromax we have always sought to keep the physical significance transparent in the formulation – for this reason. the values are the same indicating that the areas under each curve from 0 to 2 are the same. This is the integral of the GZ curve where the ordinate is the area under the GZ curve integrated from zero to the heel angle in question. The capsizing moment is taken as the magnitude of GZ at this tangent heel angle 2 . Finally since the dynamic heeling arm is a straight line with constant slope we know that the corresponding heeling arm is a constant value. From these facts we can derive the following GZ and heeling arm curves:
Page 295
. This is the dynamic heeling arm curve (blue) and is the integral of a constant value heeling arm. The problem is to reformulate this so that this capsizing moment can be found from the GZ curve:
Dynamic stability curve and Dynamic heeling arm. we have tried to distil the essence of the various stability criteria and present them in their simplest form whilst preserving the physical significance of the stability characteristic under assessment.
From the figure above we can see that the slopes of both curves are the same at 1 and 2 .
Capsizing moment
Often a capsizing moment is determined from the dynamic stability curve by drawing a line through the origin which is tangent to the GZ area curve. Remembering this relationship and that the slope of the dynamic stability curve is the value of GZ it is often possible to reformulate the same criterion in terms of one based on the GZ curve.Appendix B
Appendix D: Specific Criteria
In Hydromax. is presented in quite different ways by different regulatory bodies.
Dynamic stability criteria
In some cases the criteria are expressed in terms of the so-called dynamic stability curve. what is essentially the same criterion. at 2 . constants such as acceleration due to gravity are explicitly shown in the formulations and consistent units are used – thus removing the need for obscure constants with strange units. In this section we look at some common criteria and demonstrate how they may be evaluated in Hydromax. In some cases. Furthermore.

Appendix F
Stability curve. Area 2 corresponds to the area under the GZ curve up to the second intercept
Knowing that Area1 = Area2 we can deduce that Area 3 = Area 4 in the figure below:
Page 296
. Area 1 corresponds to the area under the heeling arm curve up to the second intercept
Stability curve.

length. (Note that the UK nautical mile is 6080ft = 1853.
Heeling arms for specific criteria ..2.6 .. Be careful as some criteria specify heeling arms and some specify heeling moments or “moments” in mass.
IMO Code on Intact Stability A.) In the following section.75(69)
3.1..Heeling due to turning Heeling moment defined by:
MR
Where:
0.2
V02 L
tonne
KG
d [kNm] 2
MR
V0
L
tonne
= heeling moment in kNm = service speed in m/s = length of ship at waterline in m = displacement in tonne
Page 297
. The approach that has been taken in Hydromax is to reflect the physics of what is generating the heeling moment. All Hydromax criteria use a heeling arm since this is what is ultimately plotted on the GZ curve.51477333.Appendix B
The magnitude of the heeling arm must be chosen so that Area 3 = Area 4
So the capsizing moment can also be determined by finding the heeling moment that gives Area3 = Area4.749(18) amended to MSC.Note on unit conversion
There are quite a few different ways in which different authorities define their heeling arms. 1929). giving a conversion multiplier for knots to m/s of 0.184m.5144444.length. To obtain the heeling arm from the heeling moment. it is necessary to divide by vessel mass. m/s. it is necessary to divide by vessel weight ( g ). the conversions for some common criteria have been explained.. Hydromax uses an internal conversion of knots to m/s based on the International Nautical mile which is defined as exactly 1852m (International Hydrographic Conference. This can easily be done in Hydromax using the GZ area derived heeling arm type 2 criterion. and in the case of “moments” in mass. Monaco. Thus 1 knot = 1852/3600 = 0.

MW.0
[m]
Where: = displacement in kg The heeling arm in Hydromax is defined as:
H
a
V2 Rg
h
[m].0
simplifying and rearranging:
a
5.196424
This section explains how the ISO 12217-1 code calculates the heeling arm and how you can replicate this calculation with a Hydromax criterion. “6. using annex D.80665 [ms-2]:
a
0.Appendix F
h L
= height of centre of gravity above centre of lateral resistance in m = waterline length of vessel in m
Thus the heeling arm is given by:
H
0.3g
2 R vkts L V2
tonnes
5.2 Rolling in beam waves and wind The curve of righting moments of the boat shall be established up to the downflooding angle or the angle of vanishing stability or 50°.196424
R L 509%
gives a value for a:
R Assuming that the ratio of the turn radius to the vessel length.0053
2 vkts
tonnes
h1
L
1000. and any ratio of turn radius to vessel length and constant a that satisfies this relationship may be chosen.0053
2 vkts
tonnes
h1
L
1000. whichever is the least.
ISO 12217-1:2002(E)
R L
0. The heeling moment due to wind. we obtain:
a
V2 Rg
h
0. the choice of a ratio of 509% merely gives a constant approaching the theoretically correct value of unity. expressed in newton metres.999798
a
Note that it suffices that .3g
R 1 1 2 L 0. = vessel speed in m/s = radius of turn in m = height of centre of gravity above centre of lateral resistance in m = non-dimensional constant (theoretically unity)
Where:
V R h a
Thus equating the required USL heeling arm to the Hydromax heeling arm. is assumed to be constant at all angles of heel and shall be calculated as follows:
Page 302
.0
finally.196424 509% 0. L
a 0.5144 1000. with g = 9.3.

where the force is calculated as 0. but shall not be taken as less than 0.3 * 72 * (72 / 21.Appendix B
MW = 0. Thus the lever is (h-H) in Hydromax should be the same as the (ALV / LWL + TM) lever from ISO. H = 0.3 * ALV * vW2.” Basically they are using moment = force * lever. TM is the draft at the mid-point of the waterline length. h = (ALV / LWL + TM). area centroid height: h = ALV / LWL + TM = 72 / 21.1 + 1. and 21 m/s for design category B.312 m.0868 m The input for Hydromax requires: Total area A = 72 m2.0. ALV is the windage area as defined in 3. the heeling moment is given as: MW = 0.3 kg/m3 Note: the centre of the windage area -h. positive up. vW = 28 m/s for design category A.3.55 LH BH = 66 m2) Thus according to the ISO 12217 formula.3 kg/m3 giving the expected result for heeling arm amplitude:
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. Hydromax‟ wind heeling arm calculation uses H for the vertical height of the hydrodynamic centre (underwater area) and h as the vertical height of the aerodynamic centre (windage area) – all measured consistently from the zero point. and the lever is (ALV / LWL + TM) This lever is a bit confusing so let‟s concentrate on that.1 + 1. You can calculate (ALV / LWL + TM) manually and then make sure the (h-H) value in Hydromax is the same by specifying: Velocity based heeling arm. a = 0.9 = 5.9) * 282 = 89961 Nm Thus the heeling arm = MW / Displacement = 89961 / 1037000 = 0.applies to the additional windage area or the total windage area depending on which option you have selected. supposing we have a vessel with the following characteristics: Displacement 105.55*LH * BH.7 tonne = 1037 kN LH 24 m BH 5 m LWL 21. For example. a = 0. Make sure you check your total windage lever in the intermediate results in the criteria results tab of the Results window.1 m TM 1.3 ALV * (ALV / LWL + TM)* vW2 Where LWL is the waterline length. expressed in metres.9 m vW 28 m/s for design category A ALV 72 m2 ( this is greater than 0.7.

1.2). Also determine the required wind speed and roll-back angle (depending on the design category) and enter these values. 6.
This section gives some details on implementing the ISO 12217 stability criteria in Hydromax. In Hydromax. positive upwards). 6. see Tables 3 and 4 (Sections 6.3: Downflooding angle Must be greater than a certain value as determined according to the design category. 2. one to check that the righting moment is sufficient and a second to determine whether the righting lever is sufficient. See also the note on converting units for the definition of the heeling arms in ISO 122171:2002(E).1.3: Resistance to waves This criterion comprises two parts. 6.4: Heel due to wind action
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. 6.
ISO 12217: Small craft – stability and buoyancy assessment and categorisation. 6.7 6.42m which is slightly greater than the height required for a category A vessel of 24m in length.3. The default value is set to 49. Verify that the angle of equilibrium does not exceed the maximum permissible value.3: Resistance to wind and waves Determine the windage area and lever and enter them in the appropriate fields in the criterion.
Part 1: Non-sailing boats of hull length greater than or equal to 6m
In many cases the user must determine the required pass value for the criteria.2) and entered into the required value field.1. H.Appendix F
Intermediate results for the wind heeling arm. which depends on the category and length of vessel being tested. An additional requirement in this section is that a specified freeboard must be exceeded. of the centre of lateral resistance at the bottom of the vessel.1. so this must be specified manually (it is measured from the model zero point.2: Downflooding height Minimum freeboard to downflooding points must be determined from Figures 2 and 3 (Section 6. the default value is set at 1. 6. Define a heeling arm and calculate the intersection of the heeling arm with the GZ curve to determine the angle of equilibrium. In most cases the default required value would exceed the worst case.3.2: Offset-load test There are several ways of evaluating this criterion: 1. there is no option for placing the height. Specify a loadcase with the offset load specified and carry out an equilibrium analysis.

2.2) and entered into the required value field. it should self right. Calculate the GZ curve with the crew seated to windward.Appendix B
Determine the parameters required for calculation of the wind heeling moment as per 6.6.6.2: Downflooding height Minimum freeboard to downflooding points must be determined from Figure 2 (Section 6. it should self right.7).42m which is slightly greater than the height required for a category A vessel of 24m in length.6: Wind stiffness test
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. the default value is set at 1. the default value is set at 1. 7.4: Stability index (STIX) Determine the required STIX value depending on the design category.2)
Part 2: Sailing boats of hull length greater than or equal to 6m
6. but note the different wind speeds to be used.5: Knockdown-recovery test The test can be approximated by examining the angle of vanishing stability in the flooded condition.5: Knockdown-recovery test The test can be approximated by examining the angle of vanishing stability in the flooded condition.3. Section 6.6.42m which is slightly greater than the height required for a category A vessel of 24m in length. Non-Sailing Boats: 6.2.6: Wind stiffness test Determine the wind heeling moment as defined in 6. this criterion will then look at the angle of equilibrium of the vessel under the applied wind heeling arm. The default value is 130.6 for the wind speed of interest (Table 6. 6. If desired you can specify the other values or let Hydromax calculate them for you. 7.3: Offset-load test This criterion is most effectively evaluated by performing an equilibrium analysis with the required offset loading condition Sailing Boats: 7.2: Downflooding-height tests Determine the required downflooding height and specify the appropriate loading condition.3: Angle of vanishing stability Determine the required angle of vanishing stability which depends on design category and vessel displacement. 6.3).2: Downflooding height Minimum freeboard to downflooding points must be determined from Figure 2 (Section 6.
Part 3: Boats of hull length less than 6m
These criteria are evaluated after an equilibrium analysis under the specified loading condition.6.2) and entered into the required value field.2. If the flooded vessel has positive GZ at the knockdown angle. see Table 5 (Section 6. 6. Determine the limiting heel angle from Table 4 (Sections 6. 6. Convert this to a heeling lever.3: Downflooding angle Must be greater than a certain value as determined according to the design category. 6. see Tables 3 (Sections 6.4. The default value is set to 40 6.2. If the flooded vessel has positive GZ at the knockdown angle.9). The criterion is evaluated after an equilibrium analysis.2. Also specify the sail area and vertical position of the sail area centroid and enter these values in the appropriate fields in the criterion.2.

6 for the wind speed of interest (Table 6.
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.6.7).Appendix F
Determine the wind heeling moment as defined in 6.6. Calculate the GZ curve with the crew seated to windward. this criterion will then look at the angle of equilibrium of the vessel under the applied wind heeling arm. Convert this to a heeling lever. Section 6.

Appendix B
Appendix E: Reference Tables
This appendix contains the following reference tables:
File Extension Reference Table Analysis settings reference table
File Extension Reference Table
The following table lists files that are used in Hydromax. For more information see the section on criteria. The library is loaded when the program starts.Links to or information on the Report
Hydromax Design
. this can be done by going to the appropriate window and saving it to a separate file.g.dcs . File
Maxsurf Design
Extension
.htk . The .Links to or information on the Results tables . is not model related. if you wish to transfer loadcases or compartment definitions from one model to another. colour When opening a .hmd file contains all the additional information that defines the Hydromax model and you need only save this file when working in Hydromax.txt
Description
Each loadcase can be saved separately The compartment definition can be saved separately The damage case definition can be saved separately All tables in the input window can be saved as text files. thickness. flexibility.hmd file does not contain: . precision.Links to or information on the Stability Criteria Library .hml . i.rtf
Library
Hydromax Criteria Library
Extension
. trimming.msd
Description
Contains control point and surface information.txt
Description
Result tables can be saved separately Results tables can not be opened in Hydromax The report can be saved separately
Report
. not when the model is opened.
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.hmd
Separate Input files
Loadcase Compartments Damage cases All Input window tables
Extension
.e. outside arrows. margin lines. sounding pipes and modulus
Output files
All Result Window tables
Extension
. Downflooding/embarkation points. E. However.hmd file with the same name. Contains hydrostatic sections information and all Input information that may also be stored separately in the files below The .Maxsurf surface information .msd file Hydromax looks for a .hcr
Description
The library is not related to the Hydromax Design File.

the trim can be substantial and the vertical separation of CG and CB needs to be taken into account.
2
The VCG is not required for the Limiting KG analysis. b) The GZ curve is calculated for the specified VCG and then the normalised KN curve is calculated as KN = GZ + VCG*SIN(heel). When calculating the LCG from a specified trim and displacement.
4
The TCG may be specified directly of derived from the lost cargo / ballast water in damaged tanks from the current loadcase. During the floodable length analysis. Analysis Settings Analyses type Trim Heel Draft DisplaceLCG TCG VCG ment
Upright stability Large Angle Stability Equilibrium Specified Condition KN values Limiting KG Floodable Length Tank Calibration S S/ FTTLC result S S / FTT S / FTT FTT S Upright R result S R R Upright Upright R result result S result result result n/a result LC LC S / LC R R R n/a n/a LC LC S / LC S/ FTT S/ FTT FTT n/a n/a LC LC S / LC S/ LC4 S/ LC4 n/a n/a For GM etc. LC LC S / LC S1 result2 S3 n/a
Where. result S R LC FTTLC FTT
Cannot be specified – they are a calculated resul Specific (fixed. the current VCG is used.Appendix F
Analysis settings reference table
The following table can be used as a reference to the various analysis settings for each analyses type.
3
The VCG is required for the floodable length analysis because of its effect on trim. a) The VCG only has an effect on the results if the analysis is free-to-trim.
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. single) value to be set by user Varied within Range specified by user Calculates values from loadcase – specifies displacement and COG only Free-to-trim to loadcase CG Free-to-trim to LCG calculated from a specific initial trim angle or specified LCG (and VCG) 1 The VCG is used in two ways in the KN analysis.

we summarize by saying that we utilize structured code. see Reference Calculations.
Reference Designs
A folder of reference hull shapes is included with Maxsurf and Hydromax. testing of the computer implementation of those algorithms. Hydromax is a complex software system of over 400. we follow a series of engineering and testing principles and procedures to ensure that Hydromax will produce results which are consistent with the level of accuracy and thoroughness a professional engineer applies to design work. To this end we follow a development and testing path which includes use of structured programming techniques. These designs are of simple geometric shapes and can be used to validate calculations performed by Hydromax.
Quality Principles
While it is impossible to ensure that any software product is completely free of bugs. Without going into the technical details of our software development methodology. testing of real world problems inhouse and beta testing in the field at Hydromax user sites. we first carry out testing on the algorithms on Reference Designs – these are proven test cases with known analytical solutions.
Structured Programming
The best defence against bugs in software is to use structured programming techniques that have been proven to improve software reliability. This following explains how Formation Design Systems has verified that Hydromax gives accurate results and what steps we take to make sure that each version of the software we ship is as reliable as possible.Appendix B
Appendix F: Quality Assurance
This appendix describes the quality assurance processes used to ensure Hydromax gives reliable and accurate results. data hiding and encapsulation and fault tolerant programming practices to enhance our software's reliability. Below is a table of results derived analytically from these shapes compared with results obtained from Maxsurf and Hydromax at different precisions. verification of the underlying algorithms.
Verification of Algorithms
When new design or analysis algorithms are introduced into Hydromax. object oriented design.000 lines of code and we believe our history of reliability reflects the effort we have put into using reliable coding practices.
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.
Quality Assurance
Many Hydromax users ask us how we know that Hydromax produces the correct results.

In the unlikely event of a problem being found. the version number may also include a letter and number suffix indicating the type and number of the release. please contact our technical support staff by email at support@formsys. it is not reliable. This involves sending the software to practicing engineers and having them use it on design work in progress to determine its reliability for actual design use.
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. we will correct it as soon as practicable. These beta testers provide us with feedback on the reliability and accuracy of the program as well as its useability and suitability for everyday work.6 1.
Testing of Upgrades
As each new version of Hydromax is released we perform a series of tests to ensure it functions correctly. Once the beta test program is completed and all testers are happy with the program. A commercial release is a completed.0d1 The first development release of version 1.5a2 The second alpha test release of version 1.5 1.
Beta Testing
Immediately prior to the release of each new version of Hydromax.
Version Control
Each new version of Hydromax displays a version number indicating the version and the date the software was first shipped. it is possible for errors to occur. we conduct a beta test of the software. debugged program reliable and ready for professional use. To get accurate results from Hydromax. These results may either come from Naval Architecture and Marine Engineering texts such as well as from other results carried out by Formation Design Systems or other engineers using other software products such as NAPA. For example 1. as with all complex software systems. It is highly experimental and not reliable.Appendix C
Testing of Implementation
Once the basic algorithms have been proven correct.64
But we're not Perfect
We make every effort to ensure that our software will meet our users' needs and perform accurately. and send you a new corrected version of the program. it is necessary for you to model the problem correctly and to correctly interpret the results produced. If you suspect a problem with Hydromax.com and explain what you believe the problem to be. An alpha release is a first public release of a program for initial testing and comment. A development version is usually only for internal use and is a very early demonstration of a possible new product or feature. A beta release is a final test version of the program released for field testing prior to commercial release. However. AutoShip etc. If the version is a development. alpha test or beta test release. we begin shipping the commercial version.64 A commercial release of version 1. It is mostly reliable but may contain some bugs.0 1. At each release the results from these tests are compared with the results from the previous release to ensure conformance with answers which have been established as being correct. testing is then carried out on more complex sample problems to which a solution has already been established using a proven analysis program.6b2 The second beta test release of version 1. It is the users' responsibility to correctly model the structure and assume responsibility for the results.